[Live-devel] RTP H.264 stream freezing on first frame using wis-streamer and VLC player

[Jeff Shanab]

Sounds like you have a good understanding of the nal units and h264 traffic
in general. So It might be a decoder issue.
I have found descrepencies in interpretations of the standard.

>From experience...
Each Nal unit needs a header before it goes to the decoder. This is the 00
00 00 01  before the nal unit. I have seen some streams only have 00 00 01
and different versions of libavcodec for example would be tolerent or not
tolerent of this.

Assuming [x] represents the nal unit  x with the headers. and 7 is sps 8 is
pps 5 is IDR slice and 1 is P-slice

[7][8][5][1][1][1]...[1][7][8][5][1][1]... is normal
[7][8][5][5][5][1][1][1]...[1][7][8][5][5][5][1][1]... is seen on high
resolution
[7][8][5][1][1][1]...[1][5][1][1]... is legal
[7][8][5][1][1][1]...[1][7][8][1][1]...[5][1][1].... is actually legal per
standard but messes with some decoders.





On Thu, Feb 13, 2014 at 9:13 AM, Eli <eli.b at bdrgroup.com> wrote:

>  Hi everyone,
>
>
>
> I have encountered a strange problem while playing an RTP H.264 stream
> using VLC player.
>
>
>
> I am developing firmware for an IP camera designed to be used with
> specialized software (control client).
>
> By default, the camera's RTSP streamer (based on wis-streamer with a
> custom video source) had a bug where in each GOP, the SPS, PPS, SEI and
> IDR-frame were all grouped, and the stream simply consisted of an SPS NAL
> unit, followed by several P-slices. The PPS, SEI, and IDR-frame were all
> hidden inside the payload of the SPS packet. This caused the target
> software to be unable to play the stream, yet VLC player worked just fine.
>
>
>
> After fixing the video source and properly splitting the various NAL
> units, the stream works properly on the target client, but now it works
> only partially with VLC - sometimes it works well, other times it freezes
> after showing 1-2 frames. Looking at the wireshark capture, the stream now
> looks like a proper H.264 stream: SPS, PPS, SEI, IDR, P-Slice, P-Slice,
> P-Slice...
>
> I've uploaded wireshark logs and VLC logs for both scenarios (old stream,
> new stream):
>
>
>
> https://www.dropbox.com/s/kk4m04toudijb82/new.log
>
> https://www.dropbox.com/s/gyg39osmhqi7p1r/New.pcapng
>
>
>
> https://www.dropbox.com/s/ewank7m3itt8jcr/old.log
>
> https://www.dropbox.com/s/jk08a4nq8cuog76/Old.pcapng
>
>
> I've posted this question to the VLC support boards and was advised it
> might be a live555 problem and that I should ask about it over here.
>
> Any help would be greatly appreciated.
>
> _______________________________________________
> live-devel mailing list
> live-devel at lists.live555.com
> http://lists.live555.com/mailman/listinfo/live-devel
>
>
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