Non-monotonous DTS in output stream and stream stall

[Daniel Schultze]

Summary of the bug:
In 2.4.3 and master/HEAD commit 00df32f6a9c497a6ec6b71cf6c2360957a6d7e6c

When publishing a live camera stream the error message:

Non-monotonous DTS in output stream and stream stall

appears and the stream stalls, depending on how far back the time stamp is the stream could be stalled for that long.

I am using ​nginx-rtmp-module to serve the stream.

How to reproduce:

% /home/danomite/bin/ffmpeg -v debug -err_detect explode -i out.flv -f flv -c:v copy -an rtmp://localhost:1935/mytv/outstream

[Daniel Schultze]

Log with errors

[Daniel Schultze]

Build log

[Daniel Schultze]

These are the step I use to make the problem happen:

1. Attempt to publish camera stream but non-monotonous warnings happen and all the players stall when that happens. (Using 2.4.3 release from my own build, the command for the build is in ffmpeg-restream.txt. The command I used is in ffmpeg-restream.txt but the log is after my rebuild)
2. Rebuild ffmpeg using master/HEAD
3. Attempt to publish camera stream via ​ffmpeg-restream.txt, but non-monotonous warnings happen and all the players stall when that happens.
4. Record the camera stream and no warning came up ​out.flv
5. Publish file to stream get some warnings and the file doesn't publish ​ffmpeg-file-to-rtmp.txt

[Daniel Schultze]

File nonmonotonous-example-10MB.flv submitted to ffmpeg ftp.

[Carl Eugen Hoyos]

Do I understand correctly that this issue is only reproducible with rtmp output?

[Daniel Schultze]

I've been able to reproduce with rtp multicast output as well.

ffmpeg -err_detect explode -rtsp_transport tcp -i rtsp://mycamera:8554/mystream -f rtp -an -vcodec copy rtp://224.0.0.1:8002 

[Carl Eugen Hoyos]

Does it also happen with file input?

[Daniel Schultze]

I have not been able to reproduce with file input.

[Daniel Schultze]

Using ​rtpdump and multicast output, as noted above, I was able to capture the time stamps going in reverse order.

To capture the stream:
rtpdump -F ascii 224.0.0.1 8002 > rtpdump.log
To parse the reverse timestamps out of the log:
cat rtpdump.log | cut -d' ' -f13 | cut -d'=' -f2 | uniq | awk '$1 > p { printf("gt ") } p = $1' | grep -v '^gt'
From the listing of the time stamps one can use less to search for them and see the contents of the stream at that point.

[Daniel Schultze]

When I re-encode the video from the camera to the same format, the error goes away.

ffmpeg -err_detect explode -rtsp_transport tcp -i rtsp://mycamera:8554/mystream -f rtp -an -vcodec libx264 rtp://224.0.0.1:8002