ffmpeg # h264_mp4toannexb

A bitstream filter operates on the encoded stream data, and performs bitstream level modifications without performing decoding.

bitstream filter作用于编码的数据，bitstream级别的修改不需要解码。

Convert an H.264 bitstream from length prefixed mode to start code prefixed mode (as defined in the Annex B of the ITU-T H.264 specification).

This is required by some streaming formats, typically the MPEG-2 transport stream format (muxer mpegts).

For example to remux an MP4 file containing an H.264 stream to mpegts format with ffmpeg, you can use the command:

ffmpeg -i INPUT.mp4 -codec copy -bsf:v h264_mp4toannexb OUTPUT.ts

Please note that this filter is auto-inserted for MPEG-TS (muxer mpegts) and raw H.264 (muxer h264) output formats.

References:

https://ffmpeg.org/ffmpeg-bitstream-filters.html#h264_005fmp4toannexb