Application Engineering and Development

Topic: Video and Sound

Topic Number: 8

Key topics / learning outcomes of this lecture

• Learn about video, compression and file size

• Learn about digital audio, sample rate and open source software for recording

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Video for Android

• What is a video?– a series of images that display in sequence to create

movement in time with the real world;– images are called ‘frames’ in video;

• How many images make a video?– a motion picture film will typically have 24 frames

display every one second;– early silent films had frame rates between 26 – 24

frames per second;• cameras were manually managed by turning a wheel holding

the film, so the camera manager could slow the frame rate down, to match the film mood!

Importance of frame rate

• 48 fps is currently being trialled in the film industry:– this will reduce flicker;

– this will reduce motion blur• motion blur occurs when images being filmed move faster in

the real world than the frame rate being captured;

• 300 fps has been tested by BBC research for use in sports broadcasts:– 300 fps can be converted to both 50 and 60 fps

transmission formats without major issues

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Image size / resolution

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In photoshop, inspect the element

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Image size: 850.8K

Width 710 pxHeight 409 px

Image compression

• This image was possibly originally around 3MB when it was first taken;

• It has been compressed to achieve an image size of 850.8KB:– this is still quite a high KB size, it could be reduced a

lot further, making transmission faster as there are less bits;

– the image could be compressed further, by running further jpeg (or other) compression algorithms on the content to reduce the size;

– the image can be made physically smaller, this will reduce the file size also;

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Video Compression

Year Standard Publisher Popular Implementations

1984 H.120 ITU-T

1988 H.261 ITU-T Videoconferencing, Videotelephony

1993 MPEG-1 Part 2 ISO, IEC Video-CD

1995 H.262/MPEG-2 Part 2 ISO, IEC, ITU-T

DVD Video, Blu-ray, Digital Video

Broadcasting, SVCD

1996 H.263 ITU-TVideoconferencing, Videotelephony, Video on

Mobile Phones (3GP)

1999 MPEG-4 Part 2 ISO, IEC Video on Internet (DivX, Xvid ...)

2003 H.264/MPEG-4 AVCSony, Panasonic, Sam

sung,ISO, IEC, ITU-T

Blu-ray, HD DVD Digital Video

Broadcasting,iPod Video, Apple TV,

2009 VC-2 (Dirac) SMPTE Video on Internet, HDTV broadcast, UHDTV

2013 H.265 ISO, IEC, ITU-T

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YouTube use H.264 codec

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Video - Flash Player

• There is no longer support for Flash Player as it is very processor consumptive and drains battery.

• Avoid designing with Flash until the issues are resolved.

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Tips to reduce video file size

• Keep the video short in terms of time;• Keep the video camera completely still where

possible, when actually filming content– compression will be more efficient if the background

of the subject remains still;

• Reduce the physical size of the video before filming, whilst keeping the aspect ratio

• Run the video through a good quality and appropriate compression technique.

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Embed Video within Android App

• Put the final video into the app resources, the res/raw folder.

• use Java to code

or

• use the YouTube

Player API

for Android

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… end of Video section…

… next is Audio …

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What is Audio

Audio used to be created by recording sound waves;

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Digital audio takes those sound waves and reproduces them digitally.

Sampling (signal processing)

• A sound wave is a continuous signal

• A sample refers to a set of values at a given point

• this is one cycle;

• this = 1hz;

• this equals

1 hz per second;

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Sound Hz (Hertz)

• The more hertz, the different the sound, known also as the pitch;

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Voice Frequency

Male 85 – 180 Hz

Female 165 – 255 Hz

Sample rate

• Sample rate for a CD is 44,100 samples from the sound wave per second;

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Decibels (Loudness)

Noise Decibels

Whisper in quiet library at 6 feet 30dB

Normal conversation at 3 feet 60dB

Normal piano practice 70dB

Loud rock concert 115dB

Jet engine at 100 feet 140dB

Death of hearing tissue 180dB

Loudest sound possible 194dB

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Creating and recording sound

Copyright issues

• when using existing sounds, ensure there are no copyright issues’

• generally, any music that was published 75 years ago becomes copyright free;

• a small sound loop of less than 3 seconds is allowed to be made from published sound which is not yet copyright free;

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Audacity

• well known open source software for sound manipulation:

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Audacity setup

• Facility to

– connect a microphone (if required);

– set up an audio host and playback device;

– select input;

– make a test recording;

– edit the recording;

– save the recording in the appropriate file format;

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Using Audio with Android

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Starting an Activity - request audio focus

Essential work for next week

• Please consult the OLE for details of:– Essential readings*

– Seminar/workshop preparation work*

– Recommended further readings

– Any additional learning

* Essential readings and preparation work must always be completed in time for the next session

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End of presentation

© Pearson College 2013