[Libav-user] Unable to decode H.264 stream received via RTMP

[Alex Cohn]

On Thu, Apr 26, 2012 at 01:53, Григорий <grishka93 at gmail.com> wrote:
> Alex Cohn <alexcohn at netvision.net.il> писал(а) в своём письме Wed, 25 Apr
> 2012 21:59:34 +0400:
>
>
>> On Apr 25, 2012 8:27 PM, "Григорий" <grishka93 at gmail.com> wrote:
>>>
>>>
>>> Alex Cohn <alexcohn at netvision.net.il> писал(а) в своём письме Wed, 25 Apr
>>
>> 2012 17:54:44 +0400:
>>>
>>>
>>>> On Wed, Apr 25, 2012 at 16:45, Григорий <grishka93 at gmail.com> wrote:
>>>>>
>>>>>
>>>>> Andrey Utkin <andrey.krieger.utkin at gmail.com> писал(а) в своём письме
>>
>> Wed,
>>>>>
>>>>> 25 Apr 2012 17:29:09 +0400:
>>>>>
>>>>>
>>>>>> 25 апреля 2012 г. 15:52 пользователь Григорий <grishka93 at gmail.com>
>>>>>> написал:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Hi all.
>>>>>>> I've built libffmpeg for Android and am trying to decode H.264 stream
>>>>>>> using
>>>>>>> it. I'm receiving that stream via RTMP connection and passing all
>>
>> video
>>>>>>>
>>>>>>> packets (excluding first byte that contains flags related to RTMP) to
>>
>> the
>>>>>>>
>>>>>>> avcodec_decode_video2 function. With H.263 it works perfectly, but
>>
>> when I
>>>>>>>
>>>>>>> try to use the same code (only with codec ID changed) for H.264,
>>>>>>> every
>>>>>>> call
>>>>>>> to avcodec_decode_video2 returns -1 and nothing gets decoded.
>>>>>>> Here is the output:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Do you know libavformat can read and demux RTMP stream by itself?
>>>>>> Seems like problem in your demuxer, because decoding the frames it
>>>>>> produces fail.
>>>>>>
>>>>>
>>>>> Yes I know, but I need more than simply receiving and playing, this
>>
>> will be
>>>>>
>>>>> a kind of VoIP service. My demuxer seems to work fine - I am able to
>>>>> successfully decode audio using Speex and video using libavcodec when
>>
>> it is
>>>>>
>>>>> encoded into H.263. Only problem is with H.264.
>>>>
>>>>
>>>>
>>>> Packing of h264 into a stream is not trivial. You may find some
>>>> curious information at
>>>>
>> http://livertmpjavapublisher.blogspot.com/2011/06/h264-avcvideopacket.html
>>>>
>>>>
>>>> Alex
>>>> _______________________________________________
>>>> Libav-user mailing list
>>>> Libav-user at ffmpeg.org
>>>> http://ffmpeg.org/mailman/listinfo/libav-user
>>>
>>>
>>>
>>> Thank you for this link. I've made it to parse the decoder configuration
>>
>> record, extract SPS, PPS and some other things. I've tried to pass PPS and
>> SPS to avcodec_decode_video2 but it still returns -1, prints "no frame!"
>> and does not decode anything else. Prepending 0x00000001 before them or
>> making AVCDCR as described here
>>
>> http://stackoverflow.com/questions/3493742/problem-to-decode-h264-video-over-rtp-with-ffmpeg-libavcodecgive
>> the same result.
>>
>> H264 decoder expects SPS and PPS to arrive together with the first (IDR)
>> frame.
>>
>> Удачи,
>> Alex
>
>
> So I'm doing the following:
> - Create a buffer
> - Get a video RTMP packet from the queue
> - Read 3 fields at the beginning of it - FLV flags (1 byte), AVC packet type
> (1 byte), and CompositionTime (24-bit integer)
> - If AVC packet type is 0, parse the rest of the packet as a decoder
> configuration record. Build AVCDCR with PPS, SPS, AVCProfileIndication,
> profile_compatibility and AVCLevelIndication and append it to the buffer.
> - If AVC packet type is 1 and there is something in the buffer, append
> packet (usually starts with 0x00000002) to the buffer, pass the buffer
> contents to avcodec_decode_video2 and clear the buffer.
> - If the buffer is empty, simply pass the packet to avcodec_decode_video2.
> At the moment when I call avcodec_decode_video2 with buffer contents (that
> consist of 2 AVCDCRs and one encoded frame), before lots of "no frame!" it
> prints "Current profile doesn't provide more RBSP data in PPS, skipping". I
> think I've made some progress but am still doing something wrong.

I will not have time to look deeper into this until next week, but
maybe you could try to use the native RMTP support in libavformat?

Alex