reader is too slow, discarding xx frames

[efraimjer]

Which version are you using?

latest-ffmpeg

Which operating system are you using?

Linux amd64 Docker

Describe the issue

I have a few cameras been encoded using medimtx and ffmpeg but now since last update i'm facing this error for each of the cameras, i've increased writeQueueSize to 65536 but i'm still having this issue then the video looks like the one below:

https://www.winnertv.com.br/highlights/690cb1a03cc8e68d3b33a08f

Describe how to replicate the issue

1. start the MediaMTX in ocean digital dedicated cpu plan with docker on an ubuntu 24.04 machine
2. publish using
   source_toencode:
   source: rtsp://ip:port/cam_id
   runOnReady: ffmpeg -thread_queue_size 2048 -i rtsp://localhost:8554/source_toencode -vf scale=-1:720 -c:v libx264 -preset ultrafast -b:v 600k -max_muxing_queue_size 1024 -f rtsp rtsp://localhost:8554/encoded
   runOnReadyRestart: yes
3. read with vlc or videojs

MediaMTX configuration

No response

MediaMTX logs

[rtsp @ 0x7ff09a469880] CSeq 11 expected, 9 received.bitrate=N/A dup=4 drop=0 speed=0.43x
2025/11/06 14:38:46 WAR [RTSP] [session f5218cbd] reader is too slow, discarding 82 frames
2025/11/06 14:38:46 WAR [RTSP] [session 24633c35] reader is too slow, discarding 512 frames
2025/11/06 14:38:46 WAR [RTSP] [session 5cbb271e] reader is too slow, discarding 39 frames
2025/11/06 14:38:46 WAR [RTSP] [session 475378ee] reader is too slow, discarding 274 frames
2025/11/06 14:38:47 WAR [RTSP] [session 8ff00cad] reader is too slow, discarding 224 frames
[rtsp @ 0x7fcdca206600] CSeq 21 expected, 20 received.itrate=N/A dup=4 drop=0 speed=0.428x
2025/11/06 14:38:47 WAR [RTSP] [session 24633c35] reader is too slow, discarding 89 frames
2025/11/06 14:38:47 WAR [RTSP] [session 475378ee] reader is too slow, discarding 409 frames
2025/11/06 14:38:48 WAR [RTSP] [session 8ff00cad] reader is too slow, discarding 238 frames
2025/11/06 14:38:48 WAR [RTSP] [session f5218cbd] reader is too slow, discarding 75 frames
2025/11/06 14:38:48 WAR [RTSP] [session 475378ee] reader is too slow, discarding 255 frames
2025/11/06 14:38:48 WAR [RTSP] [session 5cbb271e] reader is too slow, discarding 125 frames
2025/11/06 14:38:49 WAR [RTSP] [session 8ff00cad] reader is too slow, discarding 488 frames
2025/11/06 14:38:49 WAR [RTSP] [session f5218cbd] reader is too slow, discarding 321 frames
2025/11/06 14:38:49 WAR [RTSP] [session 5cbb271e] reader is too slow, discarding 237 frames
2025/11/06 14:38:50 WAR [RTSP] [session 8ff00cad] reader is too slow, discarding 64 frames
2025/11/06 14:38:50 WAR [RTSP] [session 24633c35] reader is too slow, discarding 237 frames
2025/11/06 14:38:50 WAR [RTSP] [session f5218cbd] reader is too slow, discarding 464 frames
2025/11/06 14:38:50 WAR [RTSP] [session 5cbb271e] reader is too slow, discarding 527 frames
2025/11/06 14:38:51 WAR [RTSP] [session 24633c35] reader is too slow, discarding 240 frames
2025/11/06 14:38:51 WAR [RTSP] [session f5218cbd] reader is too slow, discarding 324 frames
2025/11/06 14:38:51 WAR [RTSP] [session 5cbb271e] reader is too slow, discarding 246 frames
2025/11/06 14:38:51 WAR [RTSP] [session 475378ee] reader is too slow, discarding 205 frames
2025/11/06 14:38:52 WAR [RTSP] [session 24633c35] reader is too slow, discarding 511 frames
2025/11/06 14:38:52 WAR [RTSP] [session f5218cbd] reader is too slow, discarding 434 frames
2025/11/06 14:38:52 WAR [RTSP] [session 5cbb271e] reader is too slow, discarding 50 frames
2025/11/06 14:38:52 WAR [RTSP] [session 475378ee] reader is too slow, discarding 342 frames
2025/11/06 14:38:53 WAR [RTSP] [session 8ff00cad] reader is too slow, discarding 421 frames
2025/11/06 14:38:53 WAR [RTSP] [session f5218cbd] reader is too slow, discarding 191 frames
2025/11/06 14:38:53 WAR [RTSP] [session 24633c35] reader is too slow, discarding 237 frames
2025/11/06 14:38:54 WAR [RTSP] [session 8ff00cad] reader is too slow, discarding 251 frames
2025/11/06 14:38:54 WAR [RTSP] [session 475378ee] reader is too slow, discarding 400 frames

Network dump

No response

[secit]

Just to confirm, when you mention "latest-ffmpeg" in the version field, did you recently update only ffmpeg, only mediamtx, or did you upgrade both at the same time?

[tnaoto]

I'm having the same Issue.
Use:
MediaMTX v1.15.4
ffmpeg is v6, which is installed in the Docker image alpine.
This also occurs whenever there is a delay in processing with opencv-python's VideocCapture.

[TagorePde]

i m having the same issue, anyone solved this?

[aler9]

Message "reader is too slow" depends entirely on the available bandwidth between the server and readers, this is not a server issue and there's not much that can be done with software only. It's like trying to make a car pass through a peephole. More infos are here:
https://mediamtx.org/docs/features/decrease-packet-loss