[FFmpeg-user] ffserver/ffmpeg (v2.5) RTSP feed errors (h264) when transcoding to libvpx

[Sergei]

Hello There,

I am having a peculiar issue with ffserver/ffmpeg v2.5 on ubuntu 14.04 
LTS (ffmpeg was installed from 
http://ppa.launchpad.net/mc3man/trusty-media/ubuntu repo).

When using my IP camera's RTSP stream as a feed I get the following 
errors (lots and lots):

[h264 @ 0x1c25540] left block unavailable for requested intra4x4 mode -1 
at 0 18 dup=0 drop=4
[h264 @ 0x1c25540] error while decoding MB 0 18, bytestream 125886
[h264 @ 0x1c25540] concealing 6049 DC, 6049 AC, 6049 MV errors in I frame
[h264 @ 0x1c25540] concealing 6394 DC, 6394 AC, 6394 MV errors in I 
framekbits/s dup=19 drop=4
[h264 @ 0x1c25540] error while decoding MB 61 53, bytestream -22te= 
232.2kbits/s dup=39 drop=4
[h264 @ 0x1c25540] concealing 1788 DC, 1788 AC, 1788 MV errors in I frame
[h264 @ 0x1c058e0] error while decoding MB 57 54, bytestream -13te= 
204.0kbits/s dup=60 drop=4
[h264 @ 0x1c058e0] concealing 1672 DC, 1672 AC, 1672 MV errors in I frame
[rtsp @ 0x1b2de40] nal size exceeds length: 14866 14251.08 bitrate= 
192.2kbits/s dup=80 drop=4
[rtsp @ 0x1b2de40] Consumed more bytes than we got! (-13441)
[rtsp @ 0x1b2de40] nal size exceeds length: 14866 1425
[rtsp @ 0x1b2de40] Consumed more bytes than we got! (-13441)
[h264 @ 0x1c058e0] error while decoding MB 106 17, bytestream -11
[h264 @ 0x1c058e0] concealing 6063 DC, 6063 AC, 6063 MV errors in I frame
[rtsp @ 0x1b2de40] Unhandled type (25) (See RFC for implementation details
[h264 @ 0x1c058e0] error while decoding MB 1 53, bytestream -60ate= 
180.9kbits/s dup=99 drop=4
[h264 @ 0x1c058e0] concealing 1848 DC, 1848 AC, 1848 MV errors in I frame
[h264 @ 0x1c05060] left block unavailable for requested intra mode at 0 
50bits/s dup=120 drop=4
[h264 @ 0x1c05060] error while decoding MB 0 50, bytestream 306898
[h264 @ 0x1c05060] concealing 2209 DC, 2209 AC, 2209 MV errors in I frame
[rtsp @ 0x1b2de40] Undefined type (31)0kB time=00:00:16.84 bitrate= 
175.1kbits/s dup=171 drop=4
[h264 @ 0x1c05060] error while decoding MB 104 22, bytestream -44
[h264 @ 0x1c05060] slice type 21 too large at 104 22
[h264 @ 0x1c05060] decode_slice_header error

If I use ffplay on other hand (or standalone ffmpeg) I do not get any 
errors.
I am already forcing the ffmpeg to use tcp.

Here is a config snippet:
<Feed front.ffm>
File /tmp/front.ffm
FileMaxSize 200M
Launch ffmpeg -rtsp_transport tcp -i rtsp://192.168.1.147:554/
ACL allow 127.0.0.1
</Feed>

<Stream front>
Feed front.ffm
Format webm
NoAudio
VideoCodec libvpx
VideoSize 960x540
VideoBufferSize 100
VideoFrameRate 25
AVOptionVideo cpu-used 0
AVOptionVideo qmin 10
AVOptionVideo qmax 42
AVOptionVideo quality good
AVOptionVideo flags +global_header
PreRoll 15
StartSendOnKey
</Stream>

When opened in the browser the stream is corrupted and drops off.
When played directly (or saved via ffmpeg without transcoding) the 
stream is perfect.

I get the same effect whether I use Launch config item, or launch ffmpeg 
manually to supply the feed.
I can also replicate the issue when attempted to transcode the stream 
into libvpx. When I transcode to stream say libx264 or mpeg2video I 
occasionally get some of those errors but not as frequent (maybe happens 
every 2000-5000 frames or so).

The source is HIKVISION DS-2CD2032-I IP camera with following settings:

Resolution: 1920x1080
Frame rate: 25 fps
Max Bitrate: 12288
Video Encoding: H.264
Profile: Main Profile
I Frame Interval: 10
SVC: OFF
Smoothing: 1

There is no packet loss the the camera (it sits on new 1Gbit/s PoE switch).

Anything I can do to work around the problem?

Thanks.

Sergei.

P.S. the reason why I installed ffmpeg out of PPA is because avserver is 
utterly broken...