[Libav-user] Libav - Is it really difficult

Tuukka Pasanen pasanen.tuukka at gmail.com
Mon Jul 13 13:23:41 CEST 2015

Just wondering why are using FFmpeg for this kind of stuff? Why not just 
send it to socket as reader ask? If I understand correctly you are not 
encoding on fly this WEBM.


13.07.2015, 13:28, Austin Einter kirjoitti:
> I am trying to use ffmpeg libav, and have been doing a lot of 
> experiment last 1 month. I have not been able to get through. Is it 
> really difficult to use FFmpeg?
> My requirement is simple as below.
> Can you please guide me if ffmpeg is suitable one or I have implement
> on my own (using codec libs available).
> 1. I have a webm file (having VP8 and OPUS frames)
> 2. I will read the encoded data and send it to remote guy
> 3. The remote guy will read the encoded data from socket
> 4. The remote guy will write it to a file (can we avoid decoding).
> 5. Then remote guy should be able to pay the file using ffplay or any 
> player.
> Now I will take a specific example.
> 1. Say I have a file small.webm, containing VP8  and OPUS frames.
> 2. I am reading only audio frames (OPUS) using av_read_frame api (Then
> checks stream index and filters audio frames only)
> 3. So now I have data buffer (encoded) as packet.data and encoded data
> buffer size as packet.size (Please correct me if wrong)
> 4. Here is my first doubt, everytime audio packet size is not same,
> why the difference. Sometimes packet size is as low as 54 bytes and
> sometimes it is 420 bytes. For OPUS will frame size vary from time to
> time?
> 5. Next say somehow extract a single frame (really do not know how to
> extract a single frame) from packet and send it to remote guy.
> 6. Now remote guy need to write the buffer to a file. To write the
> file we can use av_interleaved_write_frame or av_write_frame api. Both
> of them takes AVPacket as argument. Now I can have a AVPacket, set its
> data and size member. Then I can call av_write_frame api. But that
> does not work. Reason may be one should set other members in packet
> like ts, dts, pts etc. But I do not have such informations to set.
> Can somebody help me to learn if FFmpeg is the right choice, or should
> I write a custom logic like parse a opus file and get frame by frame.
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