I'm streaming mp4 video files (some of them are avi converted to mp4 with ffmpeg earlier) over udp://232.255.23.23:1234 from linux (embedded) with ffmpeg v3.4.2 to multiple linux (antix) machines that play the stream with MPV, all of this happens in local network so I expected it to work flawlessly, but unfortunately it doesn't.
Here are the original commands I tried to use:
ffmpeg
ffmpeg -re -i PATH_TO_FILE.mp4 -c copy -f mpegts udp://232.255.23.23:1234
mpv
mpv --no-config --geometry=[geo settings] --no-border udp://232.255.23.23:1234
This seemed to woork good, however a problem appeared that on the displaying end, the stream is actually much longer than the streamed content itself. The mp4 files in total have ~5 minutes 36 seconds, and mpv plays the entire stream loop in >= 6 minutes. I think it's happening because of dropped frames, that mpv waits to recover or something and therefore extends the length of the actual content. This cannot work in my case, as I have a precise time gap for displaying the stream and it cannot be longer than the streamed content. All the content is made in 1680x800 resolution and is displayed on a screen with 1680x1050 resoltion (positioned with mpv geometry)
It appears that using this command for mpv:
mpv --no-config --framedrop=no --geometry=[geo settings] --no-border udp://232.255.23.23:1234
made the duration correct, however this introduces huge artifacts in the videos sometimes.
I read that using -re for streaming can cause these frame drops, so I tried putting a static number of fps for both file input and output stream, for example:
ffmpeg -re -i PATH_TO_FILE.mp4 -c copy -r 25 -f mpegts udp://232.255.23.23:1234
This reads the file at native framerate and outputs the stream at 25fps, and it appears to have the timing duration correct, but it also causes occasional articats and I think has worse qualit overall. Output from mpv when one of the artifacts happened:
[ffmpeg/video] h264: cabac decode of qscale diff failed at 85 19
[ffmpeg/video] h264: error while decoding MB 85 19, bytestream 85515
I also tried using --untimed or --no-cache in mpv, but this causes stutters in the video
I'm also getting requent Invalid video timestamp warnings in MPV, for example: Invalid video timestamp: 1.208333 -> -8.711667
Playing in mpv without --no-config and with --untimed added also causes frequent artifacts:
V: -00:00:00 / 00:00:00 Cache: 0s+266KB
[ffmpeg/video] h264: Invalid NAL unit 8, skipping.
V: -00:00:00 / 00:00:00 Cache: 0s+274KB
[ffmpeg/video] h264: Reference 4 >= 4
[ffmpeg/video] h264: error while decoding MB 6 0, bytestream 31474
[ffmpeg/video] h264: error while decoding MB 78 49, bytestream -12
V: 00:00:06 / 00:00:00 Cache: 5s+11KB
Invalid video timestamp: 6.288333 -> -8.724933
V: -00:00:05 / 00:00:00 Cache: 3s+0KB
[ffmpeg/video] h264: Invalid NAL unit 8, skipping.
[ffmpeg/video] h264: error while decoding MB 59 24, bytestream -27
V: -00:00:04 / 00:00:00 Cache: 3s+0KB
[ffmpeg/video] h264: Reference 4 >= 3
[ffmpeg/video] h264: error while decoding MB 5 2, bytestream 13402
V: -00:00:03 / 00:00:00 Cache: 2s+0KB
[ffmpeg/video] h264: Reference 5 >= 4
[ffmpeg/video] h264: error while decoding MB 51 21, bytestream 9415
I tried playing the stream with ffplay and it also caused the videos to be "played" 20 seconds longer. Is there any way to keep the streaming duration intact and prevent those huge artifacts? These aren't any huge video files, they are few MB each, everything happens in local network so the latencies are minimal.
Output from ffmpeg when streaming one of the files:
libavutil 55. 78.100 / 55. 78.100
libavcodec 57.107.100 / 57.107.100
libavformat 57. 83.100 / 57. 83.100
libavdevice 57. 10.100 / 57. 10.100
libavfilter 6.107.100 / 6.107.100
libswscale 4. 8.100 / 4. 8.100
libswresample 2. 9.100 / 2. 9.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'SDM.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf57.48.100
Duration: 00:00:20.00, start: 0.000000, bitrate: 1883 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1680x800 [SAR 1:1 DAR 21:10], 1880 kb/s, 24 fps, 24 tbr, 12288 tbn, 48 tbc (default)
Metadata:
handler_name : VideoHandler
Output #0, mpegts, to 'udp://232.255.23.23:1234':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf57.83.100
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1680x800 [SAR 1:1 DAR 21:10], q=2-31, 1880 kb/s, 24 fps, 24 tbr, 90k tbn, 25 tbc (default)
Metadata:
handler_name : VideoHandler
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
frame= 480 fps= 24 q=-1.0 Lsize= 5009kB time=00:00:19.87 bitrate=2064.7kbits/s speed= 1x
video:4592kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 9.082929%
Edit: all the files don't contain any audio, so it should be even less traffic on the network
