Opened 3 years ago
Last modified 2 years ago
#8889 new defect
mpegts with dvb_subtitle on udp output broken?
|Reported by:||barhom||Owned by:|
|Blocking:||Reproduced by developer:||no|
|Analyzed by developer:||no|
Summary of the bug:
Input video has dvb_subtitles;
Use mpegts muxer and copy subtitles to output using udp;
The output is bad.
Does not happen when outputting to file instead of udp. And it does not happen if you choose to omit the subtitles.
How to reproduce:
Unfortunately I could not make the test file small and still present the issue. The input.ts file you need to download is 53M.
The following reproduces the bug.
ffmpeg -re -i "input.ts" -c copy -map 0:v -map 0:a:0 -map 0:s:0 -f mpegts "udp://126.96.36.199:1231?pkt_size=1316"
In order to "watch" the issue I recommend watching the output using either VLC or MPV using the link "udp://@188.8.131.52:1231".
Should you choice to remove the subtitles like this,
ffmpeg -re -i "input.ts" -c copy -map 0:v -map 0:a:0 -f mpegts "udp://184.108.40.206:1231?pkt_size=1316"
The issue will not present itself.
You might want to remove the "-re" and record the multicast using the "multicat" tool back to file if you need to investigate further.
Change History (3)
comment:1 by , 2 years ago
comment:2 by , 2 years ago
Patch provided by rcombs seems to solve this issue,
comment:3 by , 2 years ago
I've added the patch in this fork,
Not sure when the patch will be released to ffmpeg.
I think I found out why I see a "glitch". It seems like when outputting to UDP there is some "waiting" time when there are no packets.
Here is an example from tcpdump. Notice how there is a 3 second delay between packets.
There is no such "delay" of 3 seconds when omitting the dvb_subtitles.