NO PART OF THIS DOCUMENT MAY BE REPRODUCED IN ANY FORM WITHOUT THE PERMISSION OF AXON DIGITAL DESIGN B.V.
EMBEDDED AUDIO PROCESSINGEMBEDDED AUDIO PROCESSINGTRANSITION OF A CHANNEL FROM SD TO HD OPERATION
With the increasing affordability of large, wide-screen displays and improved compression technologies enabling more picture information to be transmitted in less data bandwidth, coupled with the need to keep up with the competition, the move from Standard Definition (SD) to High Definition transmission (HD) operation is now under way in many parts of the world. This brings with it challenges and great opportunities.
Unless a channel is in its start-up phase and is not intending to use legacy material it will almost certainly have to make provision for both SD 4:3 and HD 16:9 media and it will also need to maintain transmissions to viewers who use SD reception equipment, at least in the medium term. Some territories have further complications in that they have produced wide-screen material in standard definition; however that will not be covered in detail in this application note.
Along with the move from SD to HD pictures and the associated change in aspect ratio the move to HD also gives the broadcaster the opportunity to enhance the viewer’s audio experience by
providing a surround sound mix to accompany the pictures.
This Application Note sets out to put forward areas for consideration by broadcasters and suggest possible migration routes from SD to HD.
Introduction
AssumptionsThe following points are assumptions that have been made in setting the framework for this document.
▪ Transmissions need to be maintained for existing SD viewers.
▪ HD transmission will be in 16:9 aspect ratio and will have both a stereo and an associated surround sound mix.
▪ SD transmissions will be in 4:3 aspect ratio and will have either a stereo or mono audio tracks with no surround sound mix.
▪ Material intended for transmission could originate in either 4:3 (legacy/SD) or 16:9 (HD) aspect ratios.
▪ Material intended for transmission may contain either a stereo (or dual mono) or surround-sound mix, or it may contain both. The surround sound mix could be recorded as either discrete tracks or as a Dolby-E bit stream.
▪ The program material may contain ancillary data in either the VBI (SD) or VANC/HANC (HD); however the handling of such data will not be covered.
Which HD?Initially broadcasters were faced with the choice of how many display lines their HD signal should contain 720 or 1080, however this choice has largely been made for them by the display manufacturers who produce the majority of new devices in a native 1080 lines (Full HD) format. There are other devices, normally the lower prices units or those which have a display area smaller than 21 inches, which accept 1080 line transmissions but display this on a screen with 768 vertical pixels.
This document assumes that HD transmission means a signal with 1080 lines that are transmitted as two interlaced fields i.e. 1080i50 or 1080i60 (actually 1080i59.95)
SD Display Picture ShapeHigh Definition (HD) video pictures will be produced in a wide-screen format and are intended to be displayed on a 16:9 aspect ratio screen. As previously stated it is assumed that existing SD
viewers will have 4:3 shaped screens; a major consideration in the migration to HD is how a wide-screen picture should appear on a 4:3 screen.
The first choice facing a broadcaster is whether it is acceptable for black bars to appear at the top and bottom of a 4:3 screen. If this not acceptable the picture will, in effect, need to be zoomed-in and approximately 14% of the wide-screen picture will need to be cropped from the sides allow it to fit on the narrower 4:3 screen. When this occurs it will be necessary to ensure the major parts of the action and any on-screen captions are contained within the area that will be displayed. With newly produced programming it should be possible to instruct the director, camera and graphics operators to shoot the program such that this occurs. However with material that is already shot or where the broadcaster has no control over how the program is made, such as with brought in series and films, it may be necessary to pan the picture to place the action the within the area to be displayed on the 4:3 screen.
Example 1:4:3 Screen displaying a 16:9 picture
Black bars at the top and bottom of the screen caused when all of the wide-screen 16:9 picture is displayed on a 4:3 screen.
Example 2:4:3 Screen displaying a 16:9 picture filling all of the available ares
Edges of a 16:9 picture missing when it is expanded to fill all of the 4:3 screen.
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Example 3:4:3 Screen displaying a 16:9 picture zoomed to 14:9
Black bars at the top and bottom of the screen reduced in size compared to example 1, but showing more of the original image than example 2.
An alternative approach is to zoom the picture slightly less than would be required in Example 2 and to allow narrower black bars to be displayed at the top and bottom of the screen. Example 3 below shows a 16:9 picture displayed as 14:9, more of the original picture is visible and there are smaller black bars when compared with Example 1 and Example 2.
HD Display Picture Shape with SD sourceStandard Definition (SD) pictures have an aspect ratio of 4:3 therefore when displayed on a 16:9 (HD) screen areas of black appear to the left and right of the picture.
In a similar manner to displaying HD material on a 4:3 screen the SD picture can be expanded to fill more of the screen area, as seen in Examples 4 and 5 below. Some broadcasters chose to replace the black areas at the sides of the screen by either static or moving colored images, commonly called curtains.
It should be noted that, unlike showing HD on SD displays where the original media has more vertical pixels than lines on the SD display, the original SD pictures will have less pixels than lines on a HD display and will therefore produce an image with reduced resolution. If this image is zoomed the resolution will be reduced further and the picture appears softer, although this will be offset to some extent by the processing quality of the up-converter.
In a similar manner to losing action and captions when displaying a expended 16:9 picture on a 4:3 screen, if a 4:3 picture is expanded so that there is no black above and below the image care should be taken to avoid the loss of action and caption information (which tend to be in the lower 1/3 of the screen).
Example 4:16:9 Screen displaying a 4:3 picture
Black bars at the side of the screen when a 4:3 picture is displayed on a 16:9 screen.
Example 5:4:3 Screen displaying a 16:9 picture filling all of the available area
Top and bottom of a 4:3 picture missing when it zoomed in to fill all of the 16:9 screen.
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Example 6:16:9 Screen displaying a 4:3 picture zoomed to 14:9
Black bars at the sides of the screen reduced in size compared to Example 4, but showing more of the original image than Example 5.
Again an alternative approach may be to zoom the picture slightly less than would be required in the Example 5 above and to allow narrower black bars to be displayed at the sides of the screen. Example 6 shows a 4:3 picture displayed as 14:9, more of the original picture is visible and there are small black bars.
AudioMany satellite and cable set-top-boxes (STB) and integrated receivers provide the facility to decode surround sound and feed this out to a number of speaker through an “AV” style amplifier system. Broadcasters can take advantage of this to enhance the viewing experience by providing “cinema like” surround sound mixes to accompany their programming.
STB are may be capable of down-mixing the surround sound to provide a stereo mix if only the inbuilt TV speakers are available.
Broadcasters need to decide if they want to transmit surround sound and, if a program does not have a surround sound mix, do they want to generate one by “up-mixing” the stereo to produce the 5.1 surround channels. The surround sound mix is commonly transmitted as an encoded data-stream using proprietary encoders such as Dolby Digital (also known as AC3).
Broadcasters will also need to decide if they will transmit just the encoded audio, a possibility if they control the supply of receivers, or do they also need to include a generically encoded audio track, e.g. MPEG1 - Layer 3, for receivers which cannot process the encoded surround sound audio track.
Operational Practices: VideoPlayout MethodologiesUnless a channel is only transmitting to HD 16:9 display equipment, and its entire media library is HD, it will need to format its output for both HD 16:9 and SD 4:3 display devices and/or also be capable of playing-out both HD and SD source material.
There are a number of frequently adopted methods of accommodating these requirements, the choice is dependent on the broadcasters existing systems, the mix of HD and SD material they intend to playout and how long mixed format operations are intended to continue.
The following is not an exhaustive description of all of the possible methodologies; it is simply intended to act as a guide to some of the possible solutions that might be adopted.
Up-conversion of SD OutputThe simplest method of providing transmissions in two different resolutions and aspect ratios is to use the existing SD program output as the only source of material for a HD 16:9 transmission system.
The broadcaster simply installs the appropriate up-converter and fixes the settings to give the desired picture shape (refer to section HD Display Picture Shape with SD material).
This method allows a quick launch of HD services however the picture quality will probably not match HD originated material and there will either be a loss of picture information if the picture is expanded and cropped to fill a 16:9 screen or there will be black bars on the sides of the screen. Schematic1 (following page) gives a visualisation of this method.
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Up-Converter
Playout Schedule
16:9 HDReceiver
SD 4:3Material
Ingest /Media
StorageSD Playout
Server4:3 SD
Receiver
SDAutomation
HDTransmission
SDTransmission
Schematic 1: Up-conversion of SD output
Dual, Simultaneous PlayoutA simple method of playing out both HD and SD material is to run two independent playout chains side by side. Each chain has all of the media in the correct format and both receive the same schedule (playlist). Whilst this provides a simple solution it is probably both the most difficult to manage operationally and also possibly the most expensive as all of the playout and transmission equipment has to be duplicated.
This methodology would also require that all existing SD 4:3 material be re-acquired as HD 16:9
and new HD material has to be down-converted to SD prior to playout.
However this method does have the advantage that if the broadcaster’s goal is to operate with only HD material and deliver their signal to only HD receivers the existing SD infrastructure can remain untouched and simply be decommissioned after the transition period has been completed.
Schematic2 gives a visualisation of the dual, simultaneous playout method.
Playout Schedule
HD 16:9Material
Ingest/MediaStorage
HD PlayoutServer
16:9 HDReceiver
SD 4:3Material
Ingest /Media
StorageSD Playout
Server4:3 SD
Receiver
HDAutomation
SDAutomation
HDTransmission
SDTransmission
Schematic 2: Dual, Simultaneous Playout
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EMBEDDED AUDIO PROCESSINGEMBEDDED AUDIO PROCESSINGTRANSITION OF A CHANNEL FROM SD TO HD OPERATION
Mixed Format Playout with SD and HD Opt-InAn advancement to the SD Playout with HD Opt-In method would be to also down-convert the HD assets to SD in real-time and switch the SD output to be fed with these at the appropriate tine. This
would however mean that there was not a complete set of assets in either HD or SD format and accurate information would need to be maintained about all assets in order that the system would run smoothly.
Schematic 3 gives a visualisation of this playout method.
Up-ConverterPlayout Schedule
16:9 HDReceiver
SD 4:3Material
Ingest /Media
StorageSD Playout
Server4:3 SD
Receiver
Automation
HDTransmission
SDTransmission
2x1SwitchHD 16:9Material
Ingest/MediaStorage
HD PlayoutServer
2x1Switch
Down-Converter
Schematic 3: Mixed format playout with SD and HD Opt-In
HD Playout with Automatic Up-conversion of SD AssetsThis method of playout uses an in-built facility, available with some video servers, to automatically detect the video standard and switch an up-converter into the output if required. This ensures that all material being output from the Playout sever is HD 16:9, achieved without user intervention. Assets are Ingested and stored in their native video standard and all are played out from the same server.
If this facility is not available a similar arrangement can be put in place using the automation to switch an up-converter into the circuit if required.
The SD transmission output uses the HD output as the source of its material; it is simply a down-converted feed of the HD output.
This methodology does not require the re-ingesting of existing material and still allows program makers to supply in SD if they cannot provide HD at this point in time.
Careful consideration needs to be given to the way native 4:3 material is handled through the system so as to avoid incorrectly shaped pictures being shown on the SD service. Another potential drawback of this method of operation is that if anything should go wrong with the up-conversion process there is no time to correct the fault before the material is played to air.
This practice is particularly suited to operations where the transition to HD operation is planned to take place over a long period the management of multiple versions (SD and HD) of the same material would cause excessive additional workload and may lead to confusion.
Up-Converter
Playout Schedule
16:9 HDReceiver
SD 4:3Material
4:3 SDReceiver
HDAutomation
HDTransmission
SDTransmission
HD 16:9Material
Ingest/MediaStorage
SD/ HDPlayoutServer
Down-Converter
Ingest/MediaStorage
Schematic 4: HD playout with automatic up-conversion of SD Assets
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HD Playout with SD material, up-converted during IngestAll material for playout is either delivered as HD or converted before it is loaded on to the HD Playout Server. This ensures that all material is conformed correctly and can be checked as being correct before playout. This also simplifies the workflow at the time of playout as all media will come from the same storage location.
Format conversion as part of the Ingest process does not necessarily require additional staffing resources, technology exists to automatically detect the format of the source material and convert it to
the required HD broadcast format without manual intervention.
As with the HD Playout with Automatic Up-conversion of SD Assets method, previously described, consideration needs to be given to the way 4:3 material is handled through the system to avoid incorrectly shaped pictures being shown on the SD service, such as a small 4:3 in the center of the frame, the so-called postage stamp effect.
Schematic 5 gives a visualisation of this playout method.
Up-Converter
Playout Schedule
16:9 HDReceiver
SD 4:3Material
4:3 SDReceiver
HDAutomation
HDTransmission
SDTransmission
HD 16:9Material
Ingest/MediaStorage
HD PlayoutServer
Down-Converter
Schematic 5: HD Playout with SD material, up-converted during Ingest
Control of Picture Aspect RatioMany broadcasters who transmit in high definition 16:9 wide-screen will also need to make provision for the transmission of existing, and also possibly newly acquired, 4:3 material. There will also be viewers who continue to view on 4:3 screens.
As discussed in Standard Definition (SD) Display Picture and High Definition (HD) Display Picture Shape with SD material there are various picture shape formatting options open to a broadcaster however care needs to be taken to avoid poorly formatted pictures.
This is an important consideration if all material is converted to 16:9 HD as part of the playout process as would be the case in the last two examples shown previously.
Many broadcasters adopt a 4:3 picture format that introduces bars at the top and bottom of the screen as part of the down-conversion process, if the original SD picture has had bars added at the sides as part of the up-conversion process the result may be a 4:3 picture surrounded by a black boarder.
Example 7: “Postage Stamp” picture following SD to HD and HD to SD conversions
SD 4:3 picture 4:3 picture up-converted to 16:9 HD with black bars
16:9 HD material down-converted to 4:3 with the addition of bars at the top and bottom of
the screen
SD to HDup-conversion
HD to SD down-
conversion
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Another example of a poorly formatted picture can occur if the SD to HD conversion is configured so that the 4:3 picture is expended to fill the whole width of the screen, with the top and bottom being
cropped. If the HD to SD conversion then crops the left and right edges of a 16:9 picture to fill a 4:3 display a considerable amount of the original 4:3 picture information would be lost.
Example 8: Cropped (zoomed-in) SD picture following two conversion processes
SD 4:3 picture 4:3 picture up-converted to 16:9 HD with top and bottom
cropped
16:9 HD material down-converted to 4:3 SD, material outside of the blue box would
not be displayed and the picture appears zoomed-in
when compared to the original
SD to HDup-conversion
HD to SD down-
conversion
The use of AFD to ensure correct picture shape formattingThe Society of Motion Picture and Television Engineers (SMPTE) define AFD (Active Format Description as follows:
”image formatting information describing certain spatial characteristics of a high definition or standard definition video image. It may be generated and carried through all or some of the video production, distribution, and emission (transmission) chain. The image formatting metadata types are Active Format Description (AFD), Bar Data, and Pan-Scan information.
AFD and Bar Data are intended to be broadcast with the video signal that they describe. AFD information is intended to guide DTV receivers and/or intermediate professional video equipment
regarding the display of video of one aspect ratio on a display of another aspect ratio”.
AFD codes embedded within the video provide a reference from which video processing equipment can determine how to process the picture shape.The AFD is a 4-bit code with another bit signifying the aspect ratio (AR) of the coded frame; this produces a naming convention of AR_AFD e.g. 4:3_1 being a full-frame picture in a 4:3 shaped frame.
Within some territories and organizations the AR element is sometimes dropped and pictures described using just AFD with assumptions about the aspect ratio. It should be noted that the example below shows what is common practice in one country, other countries and organizations may adopt different interpretations of AFD or insist on only using AFD in combination with AR information.
Examples of AFD values:
▪ AFD 0 = As coded frame, this is used if some material may still have AR information ▪ AFD 1 = 4:3 Full-Frame in a 4:3 Frame ▪ AFD 2 = 16:9 Full-Frame in a 16:9 Frame ▪ AFD 3 = 14:9 Image with bars top and bottom ▪ AFD 4 = Reserved ▪ AFD 5 = 4:3 Full-Frame with may be cropped to 14:9 for wide-screen display
OR ▪ AFD 5 = 4:3 Image with bars to either side ▪ AFD 6 = 16:9 Full-Frame with may be cropped to 14:9 for display on a 4:3 screen ▪ AFD 7 = 16:9 Full-Frame with may be cropped to 4:3 for display on a 4:3 screen
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Devices such as up/down-converters and aspect ratio converters (ARCs) can be configured to detect the AFD and convert the picture shape to match that required for the intended display shape. SMPTE
standard, SMPTE 2016-1 Format for Active Format Description and Bar Data defines the origination and carriage of AFD.
Example 9: HD material intended for viewing on a 4:3 screen processed differently depending on the source of the original material
SD to HD Up-conversion with AFD = 16:9_7 HD to SD Down-conversion with AFD = 4:3_1
Original 16:9 HD picture with AFD = 16:9_2 HD to SD Down-conversion with AFD = 4:3_3
Example 9 shows how the AFD code embedded with the picture is used by the down-converter in the SD transmission chain to adjust the aspect ratio of the SD picture depending on the source of the original HD material.
By detecting that the HD material was originated from an SD source the down-converter could adjust the output to remove the black bars or if it was native HD it can produce a 14:9 image.
The AFD codes can be carried in different manners within the video, traditionally in SD systems the AFD is carried as a modified WSS (extended WSS) signal which is a luminance signal on the first half of SD line 23 (625 line systems). Some transmission devices such as MPEG encoders do not recognize WSS and therefore the same information
is carried as Video Index on low-significance bits in the chrominance information during the vertical blanking, commonly on Line 11.
WSS has the advantage that the information can be carried on both digital and analogue system and because it is part of the first active video line it will pass through a wide range of broadcast equipment. However because of the signals close proximity to active picture with only a minor downward shift of the picture this high level luminance signal will become visible especially on LCD and Plasma TVs which do not over-scan the picture.
In HD it is possible to map the AFD information into a data packet following SMPTE Standard 2016-3-2007, this data is carried in the ancillary data space (ANC) alongside the video information.
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Operational Practices: AudioSurround Sound AudioAlong with the improved picture quality HD transmission also offers the possibility of having more than just mono or stereo sound. HD receivers often have a processor that can produce 6 or 8 audio outputs allowing the position of a sound source to be localized both in front of and behind the listener. The surround sound is transmitted to the viewer as an encoded data stream using a compression technology like Dolby Digital Plus.
Not all HD viewers will have surround sound speaker setups in their home and SD reception technology may not be capable of handling surround sound transmissions therefore a broadcaster may need to maintain a mono/stereo audio output alongside any surround sound operations.
Within a broadcast facility the operator has a choice of how the surround sound audio is handled, originally a large proportion of broadcast equipment could not record or process more than 4 audio tracks, to overcome this Dolby developed a system whereby up to 8 audio tracks could be lightly compressed and carried in the data space of 1 AES pair, this is known as Dolby-E. It should be noted that Dolby-E is not an audio signal but a compressed multi-channel audio data-stream that can be carried through AES or SDI infrastructure. To monitor or process audio in the Dolby-E bit-stream the stream has to be decoded.
Many broadcast devices now have 8 or more audio tracks and so it is now possible to handle surround sound audio as discrete tracks without the need to combined then all into one data-stream, although doing so has the advantage that all of the audio that goes to make up the surround mix is kept together. Another advantage is that by compressing the audio tracks a transmission system can carry up to 8 separate surround sound mixes, each mixed in a different language.
Each Dolby-E encode or decode stage takes at least the same time period as 1 video frame and therefore each processing stage has to be accompanied with a suitable delay in the video signal to ensure continued synchronization between picture and sound.
Not all program material will have a surround sound mix, however advanced audio processors are
available which can detect the absence of surround audio and provide an up-mix based on analysis of the stereo audio.
Control of Audio LoudnessBroadcasters specify the nominal audio operating level to which a program should be mixed, e.g. -18dBfs, and also the absolute maximum audio level which a program may not exceed e.g. -10dBfs, however this does not prevent a viewer experiencing differences in perceived audio level between the various pieces of material being transmitted on the same channel. The perceived audio variation can be caused by a number of factors such as the type of material (speech/music/sport) being transmitted and how heavily the audio has been processed by devices such as compressors, limiters etc.
This perceived audio level is termed loudness and in some territories broadcasters are mandated to ensure that the variation in measured loudness between all of the material on a channel is keep within strict limits an example of this being the Commercial Advertisement Loudness Mitigation (CALM) Act in the USA.
Audio processors can be used to adjust the level of the audio using pre-defined algorithms, these are commonly installed in the media reception and Ingest area to ensure all stored material is corrected before transmission. However material could be delivered as complete files or the channel might carry live broadcasts both of which may need adjustment as part of the playout process.
If the broadcaster is using Dolby Digital as the method of delivering surround sound to the viewer they will be required to produce metadata defining the audio tracks that are being carried in the data stream. As part of this metadata a broadcaster has to specify a value for Dialog Normalization (Dialnorm) which is used by the receiver’s decoder to change the audio output level depending on the value. A broadcaster would set the Dialnorm for an action movie to be lower than that for a speech program, when these are received the equipment adjusts the output level to produce a consistent volume for the viewer. Many automation systems provide the facility to control the metadata values inserted into the output Dolby Digital data-stream on a program by program basis allow broadcasters to easily manage their audio output levels.
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Access Services (Closed Captioning and Audio Description) In additional to the audio and video associated with the program a channel may also wish to provide facilities for viewers with poor hearing or limited eye-sight. Close captions are a textual representation of a programs dialog and sound effects; they are normally produced off-line and played out in synchronicity with the program. In an HD systems they are normally carried within the VANC following OP47; defined as part of the specification for Free
TV Australia but widely adopted in countries with PAL SD standards or they transmitted using the EIA708 standard used mainly in North America and other countries that previously used NTSC.
Audio Description adds a narrative to the program audio to provide additional detail about the on-screen action for people with limited eye-sight. It is an additional pair of audio tracks, one carrying a description of the on-screen action and a second to indicate to the reception equipment when to dip the program sound and output the description.
Axon SolutionsSynapseAxon produce a wide-range of modular interfacing products which have been, and are being, deployed by a large number of broadcasters and playout facility providers as part of their transition from SD to HD operation.
Axon’s Synapse range provides problem solvers in all the major functional groups including; signal distribution, synchronization, up/down-conversion, surround sound processing, audio loudness adjustment, video legalization and data-bridging.
IngestThe first example shows a possible Ingest processing configuration which corrects illegal
colors (HDL200) and also adjusts the audio level to give a consistent loudness (DLA44) as the material is being Ingested. Also shown is an up-converter which will automatically detect SD and up-convert to the desired standard and a Dolby-E decoder which detects Dolby-E and decodes to discrete channels. If there is no Dolby-E it routes the normal PCM stereo audio through the card.
The DLA44 has an upmix function which can be programmed to generate a surround sound mix from the stereo PCM if it does not detect a audio on the surround sound input.
Schematic 6 gived a visualisation of the described setup, with a HSU05 up converter and DBD18 Dolby E decoder.
Schematic 6: Ingest processing with video legalising and loudness control
Up Converter
Dolby-E Decoder
Video Legalization
AudioLoudness Correction
SOURCE VTR
INGEST SERVER
SD or HD Video with embedded audio (and
Dolby-E)
Legalizer de- embeds the audio and passes this to
the Audio Loudness
Corrector (via Dolby-E decoder if
required)
Dolby-E Decoder to convert to discrete audio
channels if required
Loudness Corrector also can produce 5.1 surround mix
from stereo source material
HSU05 HDL200
DBD18
DLA44
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The second example shows a similar system with the addition of a DBE08 Dolby-E encoder should the broadcaster chose to carry surround sound mixes through the playout operation in an encoded form to reduce audio channels or to ensure that all of the audio elements are handled together.
It is important that the Dolby-E data packets are time aligned with the video frames there are
embedded in and do not “over-lap” into adjacent frames. If this situation occurs when the signal is switched in a router or Presentation Mixer audio disturbances would be detected. Axon produce an alignment tool HES20 which de-embeds Dolby-E packets, automatically aligns these with the video frames and accurately re-embeds to ensure the correct timing relationship between video and Dolby-E packets is maintained.
Up Converter
Dolby-E Decoder
Video Legalization
AudioLoudness Correction
SOURCE VTR
INGEST SERVER
SD or HD Video with embedded audio (and
Dolby-E)
Legalizer de-embeds the audio and passes this to the Audio Loudness Corrector (via Dolby-E decoder if
requireed)
Dolby-E Decoder to convert to discrete audio
channels if requiredLoudness Corrector also can
produce 5.1 surround mix from stereo source material
HSU05 HDL200
DBD18
DLA44
Dolby-E Alinger
HSE20
Dolby-E Encoder
DBE08
Dolby-E Encoder to convert discrete audio channels to Dolby-E
stream
Video/Dolby-E data alignment tool
Schematic 7: Ingest processing with video legalising, Dolby-E encoding and loudness control
Contribution Circuits (Incoming–Lines)In SD operations most incoming circuits where stereo and simply required synchronization to align the signal to the station timing. In HD operations there is still a requirement for synchronization but the incoming signal may be SD requiring up-conversion and the circuits may have a limited number of audio tracks necessitating the use of Dolby-E encoding to carry a surround sound mix from the remote location to the broadcast station.It should be noted that synchronization may not just be limited to aligning the incoming pictures with the station reference point but also correcting any audio/video timing (lip-sync) errors that might have occurred along the contribution path.
Axon produces a range of both up-converters and frame synchronizers. The HSU05 is a low latency cost-effective up-converter which monitors the input video standard and automatically adjusts it for the correct standard at the same frame rate. If the incoming signal might be originated in any
world TV standard an advanced cross-converter would be required such as the HXH110 which would also provide the frame synchronization function.The HEP100 automatically detects the presence of Dolby-E and decodes it to discrete audio channels.HFS110 is one of a range of frame synchronizers; it has audio shuffling and embedding functionality and can independently delay the video or the audio to correct for A/V timing issues.
The Synapse rack mount frame has a patented internal bus structure (Synapse Bus) which allows Synapse Add-On audio I/O cards to be placed alongside Master modules, in this example the HFS100 frame synchronizer, to provide connectivity and additional processing (such as audio sample rate conversion). The Master modules have the embedding (or de-embedding) functionality to utilize the audio signals from the Add-On cards. By adding 2 x DIO48 cards to a HFS110 it is possible to embed a total of 8 AES pairs, 16 audio tracks, in total.
DIO48
DIO48
Dolby-E DecoderUp-ConversionInput SDI or HD-
SDI
HSU05 HEP100House Router
Studio 2 Router
Pres Router
FrameSync etc.
HFS110
AES
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Presentation (Playout)Presentation, or the playout out, of a channel is, by necessity, tailored to the requirements of the channel and therefore it is difficult to propose an off-the shelf solution however the Synapse range of modules provides a comprehensive array of the building blocks required for a successful system. They have been tested over many years and are in
use in a wide range of channels watched by 10s of millions of viewers daily.
The schematic below shows a typical automated playout system and brief details of each of the modules is given below. It should be noted all audio processing is accomplished in the embedded domain.
Mixer/Keyer
Logo Store
Key/Fill 1
Key/Fill 2
Program
Preset
External Audio
PreviewMonitoring
EmergencyRouter
Pres Router Tie Lines
Pres Router
ChannelBranding
V/O Mixer Databridge OutputEncoders (HD)
HLI20
HVO10 HSI10HDK150
TX DownConverter &Redundancy
Switch
HXT12
SignalChecking &Redundancy
Switch
2HX10
Dolby-DigitalEncoder
HPD100
GXP880 SignalChecking
2HX10
HD
SD OutputEncoders (SD)
SubtitleSystem
External Audio
HDK150: The Mixer/Keyer module is the heart of the presentation system. Many situation do not require a full featured presentation mixer, although manual control can be achieve by use of a custom soft control panel on the Axon Cortex control and monitoring system (requires –PV option) or by the recently shown hardware panel. The HDK150 takes 4 video feeds from a central router and provides the ability to mix between sources, key 1 or 2 sources over others and mix the audio from all sources and external inputs together – the majority of the functionality required in a Presentation mixer, all contained on a single module. If a video squeeze-back option is required the HDK200 module can provide this in addition to all of the other functionality describer here.
HLI20: Channel branding module, it has two separate logo keyers, each using CF storage. Logos can be static or moving animations, one of the logos can be substituted by an in-vision clock if required. When used in combination with the HDK150 or HDK200 a preset based presentation system can be assembled in just two modules.
GPX880: Axon has recently introduced a module HD router, based on the standard Synapse module form-facture, each card provides 8-inputs and 8-outputs, within the space of 5 modules it is possible to construct a 40 x 40 routing system. In the this example a combination of GPX880 modules have been used to make-up a local emergency router to be used if the main routing system fails or the system requires re-configuration. The modular nature of the Synapse routing solution means that a system can start off small and be added to when the need arises.
2HX10: Very few modern playout systems are staffed on a 1 to 1 basis, Presntation personnel are required to operate and monitor a number of channel simultaneously and therefore provision needs to be made to alert operators to developing issues with signal quality, picture freeze, audio loss etc. The use of a 2HX10 module provides two import functions within one card; a 2x1 switch to allow a back-up feed to be taken to air in an emergency and it also has two channels of advanced monitoring providing error detection and alarms for operators in a multi-channel environment.
HVO10: This module provides an embedded audio mixer with 4 AES inputs allow the operators to add external audio to the normal program sound; for instance to provide announcements or play music over static images.
HSI10: Modular databridge able to insert data, such as subtitles, into the VANC
HXT12: This multi-functional card is a good example of the way Axon has combined functionality typically requiring many cards on to a single module. The card has a 2x1 switch which, in the example, is being used to bypass various other modules should work be required on the transmission path, it also has a high quality down-converter, with ARC, and separate HD and SD frame synchronizers allowing individual adjustments of output timing. The module also has separate HD and SD audio embedders should it be necessary to add audio to the program streams at this stage.
HPD100: Embedded Dolby Digital Encoder, this module extracts the discrete audio tracks that will used to form a Dolby Digital transmission stream and encodes them back into the HD-SDI program. The module als0 has 16 tracks of audio shuffling.
Axon application note page 13/18
EMBEDDED AUDIO PROCESSINGEMBEDDED AUDIO PROCESSINGTRANSITION OF A CHANNEL FROM SD TO HD OPERATION
Alternative ModulesAxon Synapse encompasses a wide-range of modular interfacing products, previous chapters have included suggested modules which provide the functionality required for various processes in the Ingest to Playout workflow. Axon recognize that one size does not fit all and, as a result, produce a range of modules each offering different connectivity, additional features and increased performance. The range covers modules providing straight-forward cost efficient functionality, through modules with independent, dual channel operation to those having a feature set traditionally requiring several cards.
Synlite - Basic building blocks, reducing expenditure where some of the more advanced processing functions are not required.
Twins - Two independent channels of advanced processing on one module reducing cost, power consumption and the rack space required to house the modules.
Advanced Performance – Modules harnessing all of the processing power of modern advanced or specialized integrated circuits.
Multi-process - Combining functionality normally requiring 2 or 3 modules into a single slot card reduces cost, saves space and power, and reduces installation complexity.
Set out below are a selection of the alternative Synapse solutions for some of the functional elements described in this document.
Up-Conversion
2GU100 – Twins card with two independent SDI or HD-SDI to 3G Up-convertersHSU05 – Synlite card providing a straight forward SDI to HD-SDI up-conversionGSU010 – SDI or HD-SDI to 3G up-conversionGSU100 – CVBS, SDI or HD-SDI to 3G up-conversion with advanced audio processingGSU150 – CVBS, SDI or HD-SDI to 3G up-conversion with advanced audio processing and video in-fill (side curtains) insertionHSU20/21 – High performance up-converter utilizing a Teranex 2 Trillion instructions per second processorHSU30/31 – High performance up-converter with advanced noise reduction utilizing a Teranex processor
Down-Conversion
2HS10/11 – Twins card with two independent HD-SDI to SDI down-converters2GS110 – Twins card with two independent 3G to HD-SDI or SDI down-convertersHDS05 – Synlite card providing a straight forward HD-SDI down conversionGDS010 – 3G to HD-SDI or SDI down-converterGDS100 – 3G to HD-SDI or SDI down-converter with advanced audio processingHDS20 – High performance down-converter utilizing a Teranex processorHXT10/12 – Targeted at playout operations these cards provide HD-SDI to SDI and CVBS conversion with individual configuration and advanced audio processing
Frame Synchronization
2GF100 – Twins card providing two independent 3G frame synchronizers each with off-set delays, color correction and audio de-embedding and embeddingHFS05 – Synlite card providing a straight forward HD-SDI frame synchronization, depending on exact module the HFS05 also provides audio de-embeddding, audio embedding or smart audio handling of embedded signalsGFS010 – 3G frame synchronizer with color correctionGFS100 – 3G frame synchronizer with color correction, off-set delay and advanced audio processing
Axon application note page 14/18
EMBEDDED AUDIO PROCESSINGEMBEDDED AUDIO PROCESSINGTRANSITION OF A CHANNEL FROM SD TO HD OPERATION
Example 10: 2 screen SynView system, comprising 6 x GQW220 modules. Larger systems can be constructed by simply adding more modules.
Monitoring and ControlMonitoring in a multi-channel, and possibly multi-standard, environment can be challenging, operators need access too easy to comprehend information, presented to them at the correct time and free from un-necessary alerts.
Typically a playout operator can be expected to manage in excess of 12 channels and be responsible for the correct loading and operation of the playlists, the availability of media and issue escalation; they no longer have the luxury of being able to constantly watch the channel’s output. They need to be quickly alerted to developing faults and rapidly be able to select alternative material or signal routing to overcome the issue.
It is no longer practicable to have 1 source on 1 screen, multi-viewers are now common place whether they are simple quad-splits or larger 16 or 24 image displays. These should also provide information about the signal’s status and accept data
inputs from the automation and other monitoring system to create a comprehensive dashboard for the operators.
Synview: multi-image processingWithin the Synapse system are a range of modules which can provide quad-splits or be combined together to form larger systems. This modular approach means that as requirements change, hardware does not become obsolete; if 8-inputs are no longer sufficient to provide the number of displays required on a multi-viewer, simply add more modules to the system. Modules are also available which have inputs for VGA and DVI signals taking data feeds from the automation, Cortex and other non-video sources.
Example 10 below shows a typical SynView system where 6 modules have been configured to feed 2 large screen displays, the first with 16 pictures and the second with 8, each having audio metering, Under Monitor Displays (UMD) and tallies.
G.P.I. I/O
REF. 1 REF. 1 LOOP
RRC/S08
ETHERNET
REF. 2 REF. 2 LOOP
RESET BOOT
FUSE
RRC/S04
FUSE
DVI OUTPUT 2
TALLY/UMD
SDI INPUTSSCREEN 2
SDI INPUTSSCREEN 1
DVI OUTPUT 1
Axon application note page 15/18
EMBEDDED AUDIO PROCESSINGEMBEDDED AUDIO PROCESSINGTRANSITION OF A CHANNEL FROM SD TO HD OPERATION
Example 11: Cortex: control and monitoring application. Primary screen.
Cortex: control and monitoring applicationAll Synapse modules have a level of signal integrity checking, even a simple HD distribution amplifier (HDR07) is able to report signal loss, the video signal’s frame rate and line standard and SDI data rates.
Specialist monitoring modules, such as the 2HX10, can detect signal defects including; picture freeze, black output, audio silence and audio clipping. This information can be used to trigger alarms via GPIs or shown in a graphical manner as part of a facility monitoring system.
Cortex, Axon’s freely available advanced control and monitoring application provides configuration and engineering monitoring tools for all of the Synapse products across a facility or wider area. It also can form the basis of a comprehensive monitoring and control system.
By adding the Panel View (-PV) option an operator can design and deploy their own customized screens, Example 13 and Example 14 illustrate how this can be used to show a transmission chain and provide a user interface for a Presentation Mixer.These screens not only give a visual indication of faults they also allow the operators to control the
relevant pieces of equipment to recover from an emergency situation.
Other options allow operators to directly control routers (-RC) with route selection being part of a graphical display. The “-SP” option allows the operator to view information from any device that conforms to the SNMP protocol e.g. broadcast equipment, IT systems, air-conditioning plant etc. in a graphical or tabulated form.
In its basic form Cortex provides an advanced graphically rich user interface presenting the configuration screens for complex modules in a straight-forward, easy to understand, manner. Example 11 shows the main navigation and configuration screen.
Cortex also provides detailed monitoring views showing a module’s current status and also the 10 most recent log enteries for that specific module. As can be seen on a 2HX10 module, shown in Example 12, color coding of the Status History Log display brings important error messages quickly to the attention of the operator. These error message are reflected on the Status screens and are represented by different colored “LEDs”.
List of devices and cards Module information Graphical module configuration screen
Axon application note page 16/18
EMBEDDED AUDIO PROCESSINGEMBEDDED AUDIO PROCESSINGTRANSITION OF A CHANNEL FROM SD TO HD OPERATION
Example 13: Cortex customized display showing a graphical presentation of a transmission chain
The display has a combination of status displays showing signal presence and aspect ratio status and control interfaces where the operator can select an alternative route via the 2x1 switches or change the aspect ratio.
Example 12: Cortex status screen showing signal status on 2IX10 module
Status history log Red log-entries and “LEDs” showing error conditions
Axon application note page 17/18
EMBEDDED AUDIO PROCESSINGEMBEDDED AUDIO PROCESSINGTRANSITION OF A CHANNEL FROM SD TO HD OPERATION
Example 14: Cortex customized interface to provide a virtual control panel for the Pres and Logo Inserter, shown in the Presentation section.
The virtual interface provides control over a number of different devices. At the top is router control, selecting the inputs to the HDK150 mixer card. The central row of buttons controls the HDK150 and allows an operator to preview the next transition. At the bottom are controls for the down-stream HLI20 Logo inserter.
The screen is completely customizable and could also contain controls for the mixing of a voice into the audio and also for selecting back-up sources.
