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• avcodec/asvenc : Don't waste bits encoding non-visible part

  22 mai, par Andreas Rheinhardt

  avcodec/asvenc : Don't waste bits encoding non-visible part
  Up until now, the encoder replicated all the border pixels
  
  for incomplete 16x16 macroblocks. In case the available width
  
  or height is <= 8, some of the luma blocks of the MB
  
  do not correspond to actual input, so that we should encode
  
  them using the least amount of bits. Zeroing the block coefficients
  
  (as this commit does) achieves this, replicating the pixels
  
  and performing an FDCT does not.
  This commit also removes the frame copying code for insufficiently
  
  aligned dimensions.
  The vsynth3-asv[12] FATE tests use a 34x34 input file and are
  
  therefore affected by this. As the ref updates show, the size
  
  and checksum of the encoded changes, yet the decoded output
  
  stays the same.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/asvenc.c
  • [DH] tests/ref/vsynth/vsynth3-asv1
  • [DH] tests/ref/vsynth/vsynth3-asv2

• ffmpeg copy a part of a video wrt to milliseconds accurately

  25 août 2016, par Santhosh Yedidi

  I am using ffmpeg to copy a part of video.

  I am using mpv to view the video. I get the start time and end time from it.

  ffmpeg -i "main.flv" -ss 01:54:34.340 -to 02:01:13.073 -c copy copied.mp4

  the problem i am facing is the video does not start from 01:54:34.340, it starts from 01:54:34.608

  so its shifting the start poistion.

  Is there any way i can start from the exact millisecond position or form that particular frame.

  or is there command to mention start frame number and end frame number. For that mpv also should tell me the frame numbers in ths OSD

  the output of the above command is

  Input #0, flv, from 'main.flv':
  
    Metadata:
  
      author          : 
  
      copyright       : 
  
      description     : 
  
      keywords        : 
  
      rating          : 
  
      title           : 
  
      presetname      : Custom
  
      creationdate    : Thu Aug 25 04:50:55 2016
  
                      : 
  
      videodevice     : VidBlaster
  
      avclevel        : 31
  
      avcprofile      : 77
  
      videokeyframe_frequency: 5
  
      audiodevice     : Realtek HD Audio Input
  
      audiochannels   : 2
  
      audioinputvolume: 100
  
    Duration: 03:55:58.86, start: 0.033000, bitrate: 855 kb/s
  
      Stream #0:0: Video: h264 (Main), yuv420p(tv), 640x480 [SAR 1:1 DAR 4:3], 819 kb/s, 30.30 fps, 29.97 tbr, 1k tbn, 59.94 tbc
  
      Stream #0:1: Audio: aac (LC), 22050 Hz, stereo, fltp, 49 kb/s
  
  Output #0, mp4, to 'copied.mp4':
  
    Metadata:
  
      author          : 
  
      copyright       : 
  
      description     : 
  
      keywords        : 
  
      rating          : 
  
      title           : 
  
      presetname      : Custom
  
      creationdate    : Thu Aug 25 04:50:55 2016
  
                      : 
  
      videodevice     : VidBlaster
  
      avclevel        : 31
  
      avcprofile      : 77
  
      videokeyframe_frequency: 5
  
      audiodevice     : Realtek HD Audio Input
  
      audiochannels   : 2
  
      audioinputvolume: 100
  
      encoder         : Lavf57.25.100
  
      Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 640x480 [SAR 1:1 DAR 4:3], q=2-31, 819 kb/s, 30.30 fps, 29.97 tbr, 16k tbn, 1k tbc
  
      Stream #0:1: Audio: aac (LC) ([64][0][0][0] / 0x0040), 22050 Hz, stereo, 49 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #0:1 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  frame=    0 fps=0.0 q=-1.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=  frame=    0 fps=0.0 q=-1.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=  frame=11906 fps=8002 q=-1.0 Lsize=   41574kB time=00:06:38.75 bitrate= 854.1kbits/s speed= 268x    
  
  video:38866kB audio:2336kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.904480%

• FFMPEG - modify only part of video with select filter

  28 janvier 2023, par Compact

  I have a video file - an NTSC DVD rip. I want to convert it into PAL DVD. The problem with that NTSC DVD is that it's a mixture of telecined content, true progressive 29.97 content, true interlaced content at 29.97 fps. The problem is with the true interlaced content - it's sometimes encoded as top field first and sometimes as bottom field first...

  


  To keep quality as much as possible, I would like remove telecined frames, but keep those interlaced sequences and turn them to 25 fps top field first. This is where the problem arises.

  


  I tried to make filter_complex chain with two select filters, where I reverse the fields for bottom field first frames, but the video is not encoding at all when I do that.

  


  Here is an example filter chain I tried to make - I've made a lot of iterations of something similar, using select or metadata select to no avail. I guess I don't understand how select and metadata select filters work. And I don't know how to do what I want.

  


  ffmpeg -i "input" -flags +ildct+ilme \
-filter_complex\
[0:v]idet,setparams=color_primaries=smpte170m:color_trc=bt709:colorspace=smpte170m \
,metadata=select:key=lavfi.idet.single.current_frame:value=bff:function=same_str,phase=b[bot];\[bot]metadata=select:key=lavfi.idet.single.current_frame:value=tff:function=same_str\
,fieldmatch=mode=pcn_ub:combmatch=full,decimate[tff];\
[tff]metadata=select:key=lavfi.idet.single.current_frame:value=progressive:function=same_str\
,fps=24000/1001[v1];[v1]select,setfield=tff[v]"


  


  If all of the interlaced content was top field first, I could simply do something similar to this :

  


  ffmpeg -i "input" -flags +ildct+ilme \
-filter:v "dejudder,fps=30000/1001,fieldmatch=mode=pcn_ub:combmatch=full,\
decimate,settb=1/25000,setpts=N/(25*TB),setfield=tff,setparams=field_mode=tff"


  


  Is that possible with ffmpeg ? To just modify a part of video and then modify it whole, including with the previous modification ?