How to transcode the parts of a segment

[captain-bugs]

I want to do ABR for LHLS. Is it possible to transcode the AnexB bitstream format directly using ffmpeg or libav libraries?
for now i'm trying to store the muxerPart.videoSamples[] data in a .h264 file.

I read if i provide the SPS and PPS as extradata to AVCodecContext i can transcode it.
But not every part has SPS and PPS only the first part of every segment.

The .h264 file which I created has order like SPS, PPS, SPS, PPS, slice of IDR, slice of non-IDR ... but only the 1st part of segment has this order the other parts only have slice of non-IDR ...

And if i want to get SPS and PPS from 1st part when i unmarshal the contents of .h264 file using h264.AnnexBUnmarshal() function i get error: NALU count (546) exceeds maximum allowed (21).
even though every au that are marshalled have the prefix of []byte{0x00, 0x00, 0x00, 0x01}

1. Is it possible to transcode the parts
2. If yes is the adding SPS and PPS as extradata to AVCodecContext right way
3. why h264.AnnexBUnmarshal() gives error

[aler9]

Hello,

Is it possible to transcode the parts

It's not always possible to decode parts, since they may not contain IDR frames. In order to start decoding a stream, you have to start from a part with the INDEPENDENT flag set to YES, after you can decode as many parts as you want.

If yes is the adding SPS and PPS as extradata to AVCodecContext right way

SPS and PPS are not enough, you need both SPS, PPS and a IDR frame. You can check the frame type by analyzing the header of each NALU contained in each access unit.

why h264.AnnexBUnmarshal() gives error

From the log entry you posted ("NALU count (546) exceeds maximum allowed (21)") it seems like there's a transmission problem between your source and the library. If you still have problems, open an issue and provide details that allow to replicate the problem, including a network dump or a sample source or a sample file.