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• PyAV : force new framerate while remuxing stream ?

  7 juin 2019, par ToxicFrog

  I have a Python program that receives a sequence of H264 video frames over the network, which I want to display and, optionally, record. The camera records at 30FPS and sends frames as fast as it can, which isn’t consistently 30FPS due to changing network conditions ; sometimes it falls behind and then catches up, and rarely it drops frames entirely.

  The "display" part is easy ; I don’t need to care about timing or stream metadata, just display the frames as fast as they arrive :

  input = av.open(get_video_stream())
  
  for packet in input.demux(video=0):
  
    for frame in packet.decode():
  
      # A bunch of numpy and pygame code here to convert the frame to RGB
  
      # row-major and blit it to the screen

  The "record" part looks like it should be easy :

  input = av.open(get_video_stream())
  
  output = av.open(filename, 'w')
  
  output.add_stream(template=input.streams[0])
  
  for packet in input.demux(video=0):
  
    for frame in packet.decode():
  
      # ...display code...
  
    packet.stream = output.streams[0]
  
    output.mux_one(packet)
  
  output.close()

  And indeed this produces a valid MP4 file containing all the frames, and if I play it back with mplayer -fps 30 it works fine. But that -fps 30 is absolutely required :

  $ ffprobe output.mp4
  
  Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 960x720,
  
                    1277664 kb/s, 12800 fps, 12800 tbr, 12800 tbn, 25600 tbc (default)

  Note that 12,800 frames/second. It should look something like this (produced by calling mencoder -fps 30 and piping the frames into it) :

  $ ffprobe mencoder_test.mp4
  
  Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 960x720,
  
                    2998 kb/s, 30 fps, 30 tbr, 90k tbn, 180k tbc (default)

  Inspecting the packets and frames I get from the input stream, I see :

  stream: time_base=1/1200000
  
  codec: framerate=25 time_base=1/50
  
  packet: dts=None pts=None duration=48000 time_base=1/1200000
  
  frame: dst=None pts=None time=None time_base=1/1200000

  So, the packets and frames don’t have timestamps at all ; they have a time_base which doesn’t match either the timebase that ends up in the final file or the actual framerate of the camera ; the codec has a framrate and timebase that doesn’t match the final file, the camera framerate, or the other video stream metadata !

  The PyAV documentation is all but entirely absent when it comes to issues of timing and framerate, but I have tried manually setting various combinations of stream, packet, and frame time_base, dts, and pts with no success. I can always remux the recorded videos again to get the correct framerate, but I’d rather write video files that are correct in the first place.

  So, how do I get pyAV to remux the video in a way that produces an output that is correctly marked as 30fps ?

• FPS drop in FFMPEG streaming processes to FB from production server

  30 janvier 2017, par Aakash Gupta

  I have made a rails app that can stream live videos to facebook rtmp server and deployed it on AWS. I have used nginx as web server. The major problem that I am encountering after viewing log files of FFMpeg processes is that sometimes the FPS of FFmpeg process starts to drop. In some cases, it remains stable at 25 FPS but in some cases, it remains at 25 only for sometime, and after that it starts to drop and sometimes it falls to even 3-4 FPS which is unacceptable during live streaming. As FFMpeg process is quite heavy, I would also like to share my CPU info as well.

  CPU information is :

  cat /proc/cpuinfo
processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 63
model name  : Intel(R) Xeon(R) CPU E5-2676 v3 @ 2.40GHz
stepping    : 2
microcode   : 0x25
cpu MHz     : 2400.070
cache size  : 30720 KB
physical id : 0
siblings    : 1
core id     : 0
cpu cores   : 1
apicid      : 0
initial apicid  : 0
fpu     : yes
fpu_exception   : yes
cpuid level : 13
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx rdtscp lm constant_tsc rep_good nopl xtopology eagerfpu pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm xsaveopt fsgsbase bmi1 avx2 smep bmi2 erms invpcid
bogomips    : 4800.14
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

  FFMPEG log file with unstable fps : https://drive.google.com/open?id=0B1gtp1iXJppkUndFamk4M0lRYzA

  FFMPEG log file with stable fps : https://drive.google.com/open?id=0B1gtp1iXJppkMkVCZEJjYWJrVTA

  When FPS was stable, I also tried to run another parallel FFMpeg process from the same server which resulted in FPS dropping of both the processes to 13-14 FPS.

  I am currently using this FFMPEG command :

  ffmpeg -loop 1 -re -y -f image2 -i "image_path" -i "audio_path.aac" -acodec copy -bsf:a aac_adtstoasc -pix_fmt yuv420p -profile:v high -s 1280x720 -vb 400k -maxrate 400k -minrate 400k -bufsize 600k -deinterlace -vcodec libx264 -preset veryfast -g 30 -r 30 -t 14400 -strict -2 -f flv "rtmp_server_link"

  I never face this problem when I try to stream to FB using app on my localhost.

  So, my questions are :

  1. What can be the reason for this FPS drop ?
  2. Can upscaling production server help me fix this issue ?
  3. Can I run multiple FFMpeg processes for streaming from same server without performance drop ?

  Thanks in advance :)

• How to embed subtitles into an mp4 file using gstreamer

  27 août 2021, par Stephen

  My Goal

  


  I'm trying to embed subtitles into an mp4 file using the mp4mux gstreamer element.

  


  What I've tried

  


  The pipeline I would like to use is :

  


  GST_DEBUG=3 gst-launch-1.0 filesrc location=sample-nosub-avc.mp4 ! qtdemux ! queue ! video/x-h264 ! mp4mux name=mux reserved-moov-update-period=1000 ! filesink location=output.mp4 filesrc location=english.srt ! subparse ! queue ! text/x-raw,format=utf8 ! mux.subtitle_0


  


  It just demuxes a sample mp4 file for the h.264 stream and then muxes it together with an srt subtitle file.

  


  The error I get is :

  


  Setting pipeline to PAUSED ...&#xA;0:00:00.009958915 1324869 0x5624a8c7a0a0 WARN                 basesrc gstbasesrc.c:3600:gst_base_src_start_complete:<filesrc0> pad not activated yet&#xA;Pipeline is PREROLLING ...&#xA;0:00:00.010128080 1324869 0x5624a8c53de0 WARN                 basesrc gstbasesrc.c:3072:gst_base_src_loop:<filesrc1> error: Internal data stream error.&#xA;0:00:00.010129102 1324869 0x5624a8c53e40 WARN                 qtdemux qtdemux_types.c:239:qtdemux_type_get: unknown QuickTime node type pasp&#xA;0:00:00.010140810 1324869 0x5624a8c53de0 WARN                 basesrc gstbasesrc.c:3072:gst_base_src_loop:<filesrc1> error: streaming stopped, reason not-negotiated (-4)&#xA;0:00:00.010172990 1324869 0x5624a8c53e40 WARN                 qtdemux qtdemux.c:3237:qtdemux_parse_trex:<qtdemux0> failed to find fragment defaults for stream 1&#xA;ERROR: from element /GstPipeline:pipeline0/GstFileSrc:filesrc1: Internal data stream error.&#xA;Additional debug info:&#xA;gstbasesrc.c(3072): gst_base_src_loop (): /GstPipeline:pipeline0/GstFileSrc:filesrc1:&#xA;streaming stopped, reason not-negotiated (-4)&#xA;ERROR: pipeline doesn&#x27;t want to preroll.&#xA;Setting pipeline to NULL ...&#xA;Freeing pipeline ...&#xA;</qtdemux0></filesrc1></filesrc1></filesrc0>

  


  My Thoughts

  


  I believe the issue is not related to the above warning but rather mp4mux's incompatibility with srt subtitles.

  


  The reason I belive this is because, other debug logs hint at it, but also stealing the subititles from another mp4 file and muxing it back together does work.

  


  gst-launch-1.0  filesrc location=sample-nosub-avc.mp4 ! qtdemux ! mp4mux name=mux ! filesink location=output.mp4 filesrc location=sample-with-subs.mp4 ! qtdemux name=demux demux.subtitle_1 ! text/x-raw,format=utf8 ! queue ! mux.subtitle_0


  


  A major catch 22 I am having is that mp4 files don't typically support srt subtitles, but gstreamer's subparse element doesn't support parsing mp4 subtitle formats (tx3g, ttxt, etc.) so I'm not sure how I'm meant to put it all together.

  


  I'm very sorry for the lengthy question but I've tried many things so it was difficult to condense it. Any hints or help is appreciated. Thank you.