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• "Missing reference picture" error when saving rtsp stream with ffmpeg

  4 mars 2020, par Cédric Kamermans

  I want to record 10 seconds of video with an IP camera via ffmpeg. The output video looks fine but i get a bunch of "Missing reference picture" errors in the log. This only happens in the beginning of the process. I also get the warning "circular_buffer_size is not supported on this build".

  I started of with the following code :

  -y -i rtsp://username:password@IP:88/videoMain -t 10 ffmpeg_capture.mp4

  But this resulted in the output being corrupted in the beginning.
  I found the following code on a forum and this seems to fix that problem. The errors still remain though.

  -y -i rtsp://username:password@IP:88/videoMain -b 900k -vcodec copy -r 60 -t 10 ffmpeg_capture.mp4

  One thing to note is that currently we’re using a C2 V3 IP camera. This model is just for testing, we will upgrade to a better model when we get this working.

  I want to clarify that i’m just beginning to use ffmpeg, so I don’t quite understand it yet. It would be greatly appreciated if someone could provide an example code of how I can fix this problem.

  Thanks in advance !

• Different results using qt-faststart and "ffmpeg -movflags +faststart"

  31 mars 2020, par Juan Ignacio Sánchez

  I have a set of videos generated by security cameras, which have the MOOV atom at the end of the file, like this :

  ftyp (32 bytes)
  
  free (8 bytes)
  
  mdat (29647845 bytes)
  
  moov (42054 bytes)

  I want to serve these files using progressive downloads (pseudo streaming) and it’s the only acceptable way to do it.

  Knowing that I tried to use tools like qt-faststart or directly ffmpeg with the corresponding flags (-movflags +faststart). Other detail is that I’m running this on a low profile machine, and FFmpeg takes like 6 8 seconds to finish (even using -c copy) and the other tool results to be much more efficient since it only moves some bytes, taking less than a second to finish. The thing here is that qt-faststart produces a video that can’t be pseudo streamed but ffmpeg does it. Here are some comparisons :

  ffmpeg :

  ftyp (32 bytes)
  
  moov (42422 bytes)
  
  free (8 bytes)
  
  mdat (29647845 bytes)

  qt-faststart :

  ftyp (32 bytes)
  
  moov (42054 bytes)
  
  free (8 bytes)
  
  mdat (29647845 bytes)

  As you can see, FFmpeg adds some extra bytes on the MOOV atom, can anyone point me in some research direction ? Thank you all.

• ffmpeg - why does hstack fail with " width not divisible by 2" When both of my inputs have even heights ?

  26 août 2020, par Nic Thibodeaux

  Here's the command I'm using to horizontally stack 2 mp4's together :

  


  ffmpeg -y  -i input1.mp4 -i input2.mp4 -filter_complex "[0:v][1:v]hstack[v]" -map "[v]" -vsync 0 stacked.mp4

  


  input1.mp4 has dimensions 594x512, and input2.mp4 has dimensions 512x512. I get this error in return :

  


  width not divisible by 2 (1113x512)
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height


  


  The confusing thing is that 1113 is such an odd number - it is not 1024, and not even 512+594 (1106). What is causing the assumed width to be such a strange value ?