[FFmpeg-user] HTTP to RTSP conversion not working, framerate issue ?

[Adam Cécile (Le_Vert)]

Hello,

I'm struggling with FFMPEG to convert a specific camera stream with 
shitty format and non-deterministic framerate to RTSP endpoint as H264.

I came up with this following command:

ffmpeg -f mxg -probesize 32 -fflags nobuffer -i 
'http://admin:admin@10.10.10.10/cgi-bin/faststream.jpg?stream=MxPEG&fps=25&jpheaderupdate=1' 
-vsync vfr -vf 'crop=iw/2:ih:0:0' -flags low_delay -preset ultrafast 
-vcodec libx264 -an -tune zerolatency -loglevel info -hide_banner 
-nostats -f rtsp rtsp://localhost::8554/7618

Producing the following output:

  [mxg @ 0x562ffddf1540] Stream #0: not enough frames to estimate rate; 
consider increasing probesize
  Input #0, mxg, from 
'http://admin:ad@10.10.10.10/cgi-bin/faststream.jpg?stream=MxPEG&fps=25&jpheaderupdate=1':
    Duration: N/A, start: 1744980937.474607, bitrate: 64 kb/s
      Stream #0:0: Video: mxpeg, yuvj420p(pc, bt470bg/unknown/unknown), 
1280x480, 1000k tbr, 1000k tbn, 1000k tbc
      Stream #0:1: Audio: pcm_alaw, 8000 Hz, mono, s16, 64 kb/s
  Stream mapping:
    Stream #0:0 -> #0:0 (mxpeg (native) -> h264 (libx264))
  Press [q] to stop, [?] for help
  [libx264 @ 0x562ffddfb380] MB rate (1200000000) > level limit 
(16711680)
  [libx264 @ 0x562ffddfb380] using cpu capabilities: MMX2 SSE2Fast SSSE3 
SSE4.2 AVX FMA3 BMI2 AVX2
  [libx264 @ 0x562ffddfb380] profile Constrained Baseline, level 6.2, 
4:2:0, 8-bit
  2025/04/18 12:55:39 INF [RTSP] [conn 127.0.0.1:57966] opened
  2025/04/18 12:55:39 INF [RTSP] [session 24e2616d] created by 
127.0.0.1:57966
  2025/04/18 12:55:39 INF [RTSP] [session 24e2616d] is publishing to path 
'7618', 1 track (H264)
  Output #0, rtsp, to 'rtsp://localhost:8554/7618':
    Metadata:
      encoder         : Lavf58.45.100
      Stream #0:0: Video: h264 (libx264), yuvj420p(pc), 640x480, q=-1--1, 
1000k fps, 90k tbn, 1000k tbc
      Metadata:
        encoder         : Lavc58.91.100 libx264
      Side data:
        cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A


It runs fine, but I cannot read anything back from the target RTSP 
server.

However, running the command with "-f mp4 /tmp/dump.mp4" produce a 
perfectly valid H264 file, with correct speed (i have timestamp 
superimposed in video).

My guess is that there is a timestamp/framerate issue but I have no idea 
how to fix that.

Can you point me to the correct direction ? Maybe ignore completely 
input framerate and generate clean native 25 fps for output ?

Thanks in advance,

Best regards, Adam.