MJPEG source -> MJPEG output quality degradation

[mvdarend]

Hi there,

Hopefully someone can help with a problem I'm having with 're-streaming' an MJPEG stream, when I do this the quality of the new stream is much worse than the original. I'm probably missing a setting somewhere but my searches haven't resulted in a solution so far. One of the software packeges we're using at the moment can only process MJPEG streams, so we're stuck with that for them time being.

The source is a sub-stream from a Hikvision camera:

When streaming this original as an RTSP stream in VLC it looks like this:

When streaming through Go2Rtc it ends up looking like this:

Here is the relevant part of the config, ffmpeg settings have been left default:

ffmpeg:  
  
streams:
  1234:
    - rtsp://User:Pass@192.168.35.201:554/Streaming/Channels/102 

I've tried playing around with all sorts of settings to no avail, anyone have an idea of what it could be?

If I set the stream from the camera to H.264 instead of MJPEG it is much better but once I try transcoding that stream to MJPEG the quality drops again to a similar level as above.

Relevant info

• Ubuntu version 23.04 running on a Proxmox VM
• go2rtc_linux_amd64 - v1.6.2
• No hardware acceleration

Edit: Spelling mistakes and better screnshot of Go2Rtc stream showing address bar.

[AlexxIT]

I have no difference in similar test for my Dahua camera.
If you share you stream - I can check it.
https://github.com/AlexxIT/go2rtc/wiki/Tunnel-RTSP-camera-to-Intenet
My contacts in github profile

[TsLenMo]

@AlexxIT I suggest adding -input_format mjpeg parameter to ffmpeg. Because some devices will provide multiple streams, the default may not be mjpeg.

[TsLenMo]

[root@localhost ffmpeg]# ./ffmpeg -f v4l2 -video_size 1920x1080 -i /dev/video0 -c:v mjpeg -an -f mjpeg out.mp4 
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 48535.066005, bitrate: 331776 kb/s
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1080, 331776 kb/s, 10 fps, 10 tbr, 1000k tbn

↑ Before (Go2RTC default parameters without -hide_banner -v error)
↓ After

[root@localhost ffmpeg]# ./ffmpeg -f v4l2 -input_format mjpeg -video_size 1920x1080 -i /dev/video0 -c:v mjpeg -an -f mjpeg out.mp4
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 48573.005768, bitrate: N/A
  Stream #0:0: Video: mjpeg (Baseline), yuvj422p(pc, bt470bg/unknown/unknown), 1920x1080, 50 fps, 50 tbr, 1000k tbn

[AlexxIT]

@TsLenMo go2rtc not using ffmpeg for transfer rtsp mjpeg to http mjpeg

[TsLenMo]

ffmpeg:
  bin: "/opt/ffmpeg/ffmpeg.sh"
  global: "-hide_banner"
  file: "-re -stream_loop -1 -i {input}"
  http: "-fflags nobuffer -flags low_delay -i {input}"
  rtsp: "-fflags nobuffer -flags low_delay -timeout 5000000 -user_agent go2rtc/ffmpeg -rtsp_transport tcp -i {input}"
  output: "-user_agent ffmpeg/go2rtc -rtsp_transport tcp -f rtsp {output}"
  # ... different presets for codecs
log:
  format: ""
  level: "info"
streams:
  linux_usbcam:   ffmpeg:device?video=0&video_size=1920x1080#video=mjpeg

this is the config file.
After I ran Go2RTC, I saw that ffmpeg's CPU usage was quite high.
I think there is a transcoding situation.

[TsLenMo]

Because my device provides two streams, one is YUY2 and the other is MJPEG. I observed that ffmpeg uses YUY2 by default.

[AlexxIT]

I think I understand more about how go2rtc works :)
@mvdarend doesn't used ffmpeg in config. So ffmpeg is not involved.

[TsLenMo]

OK, Sorry.

[AlexxIT]

@TsLenMo your config wrong. If your USB camera supports MJPEG, of course you should use input mjpeg. Check WebUI

[TsLenMo]

Thanks.

[AlexxIT]

Please let me know if the problem is relevant

[Fohdeesha]

I have the exact same issue, with the exact same type of degradation in the image - I also have a hikvision camera, so probably something weird with their mjpeg streams over rtsp? I will open the rtsp feed from the camera so you can check it yourself as requested, I will message you the link.

[Fohdeesha]

@mvdarend - After giving @AlexxIT access to my hikvision stream, he confirmed hikvision has a weird non-standard mjpeg stream implementation, and quickly implemented a fix for handling it - now my streams look identical. The change is in the master branch, you can get a binary of it here - https://nightly.link/AlexxIT/go2rtc/workflows/build/master

[AlexxIT]

https://github.com/AlexxIT/go2rtc/releases/tag/v1.9.5