Digital video and audio can be represented digitally through sampling sound waves and images into discrete values. Key aspects that were discussed include: 1) Digital audio is represented through samples of sound pressure taken at regular intervals described by sample rate, sample format/bit depth, number of channels, and compression codecs. 2) Digital video also samples images over time described by frame size, frame rate, color space, chroma subsampling, and video codecs. 3) Audio and video streams are often combined into digital container formats for storage and transmission, with some examples given like MP4, Matroska, and Ogg.

2. ‫الرحیم‬ ‫الرحمن‬ ‫الله‬ ‫بسم‬
Seyed Rahim Firouzi

3. Digital Video and Audio
Seyed Rahim Firouzi

4. Digital Video and Audio
Very Hard
“only ninja can do it”

5. Digital Video and Audio
Sound:
In physics, sound is a vibration that
typically propagates as an audible
wave of pressure, through a
transmission medium such as a gas,
liquid or solid.(wikipedia)

6. Digital vs Analog
● Noise
● Transfer,Storage,Copy,Play (Quality)
● Compress
● Analyze & tools
● continually

7. Audio
Sample rate(Hz):
Human sensitivity(20Hz -20Khz)
8k ,16k ,32k ,44.1k ,48k
aliasing
A-law ,U-lav
raw PCM :Pulse Code Modulation
PDM :Pulse Density Modulation

8. Audio
Sample format(bit)
8bit,16bit,24bit,float
Endianness
Little endian ,Big endian
Channel count
Mono (1) ,Stereo (2) ,surround sound
Compress ( ? )
Lossless vs lossy compression ,DCT,….
Bit Rate(bit/s)
List of codecs
FLAC,ALAC,G711,G721,G729,mp1,mp2,mp3,aac,Vorbis

9. Video
Video ?
…...
Audio f(t) video f(x,y,t) → color

10. Video
Size (pixel x pixel or count)
Width X height
aspect (A:B)
4:3 16:9 ….
Frame rate(fps)
Human sensitivity(48 fps)
Pal = 25,ntsc=30, pc = any
Interlacing(vs Progressive)

11. Video
Color Space
RGB
Red ,blue ,green
YUV(YCrCb)
luma (y) chrominance (UV)

12. Video
Chroma subsampling(A:B:C)
compress (?)
60 minute HD 25 fps 24bit
size= 3600*1920*1080*25*3=559,872,000,000 byte
Band width=1,244,160,000 bit/s

13. Video
List of codecs
h.264 lossless ,vp9 ,mpeg1 ,mpeg2 ,mpeg4 ,h.264 avc ,hvec
,Theora

14. Digital Video and Audio
Digital container format
A container or wrapper format is a metafile
format whose specification describes how
different elements of data and metadata coexist
in a computer file.(wikipedia)
List of Container
Wav ,Matroska/webm ,ogg(ogv,oga), mp4,

15. Streaming
Live Streaming
Protocol :RTP ,RTCP (h323,sip,rtsp) ,RTMP ,HTTP Live Streaming
Video and Audio Tag in html5

16. ?