Video surveillance industry G711 codec [continued] collection knowledge, video surveillance g711

Video surveillance industry G711 codec [continued] collection knowledge, video surveillance g711

1. reference factors for Buffer collection:

A. How long does the buffer take, for example, ms or 50 ms;

B. The number of bytes received per second;

BufferSizeM = dwBytesPerSec * dwLatencyInMilliseconds/1000;

2. Examples:

Collect sound: If the encoding format is G711

BufferSize = 16/8*8000*(TimeMs)/1000

Note:

16/8 occupies 2 bytes for each Sample of G711,

8000 indicates the sampling rate, that is, 8000 samples of G711 need to be sampled every 1 s,

TimeMs is buffer time (ms), assuming TimeMs is 50 ms,

Then BufferSize = 2*8000*50/1000 = 800 Bytes, that is, the size before compression is 800;

In this way, the size of each package after G711 compression is 400 Bytes.

3. How long does the standard practice usually take?

TimeMs * sampling frequency.

For example, 20*8000/1000 = 160 (20 is PTime, 8000 is the sampling frequency). Generally, a single frame of audio data is 20 ms, which improves the playback latency.