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• avformat/movenc, segafilmenc : Remove unnecessary avio_tell()

  16 janvier 2020, par Andreas Rheinhardt

  avformat/movenc, segafilmenc : Remove unnecessary avio_tell()
  When the faststart option for the mov/mp4 muxer is used, the current
  
  position (i.e. the size of the already written data pre-shifting) was
  
  evaluated twice : First in an initialization and then again later,
  
  overwriting the first value without having ever touched it. So remove
  
  the initialization.
  Also, the clone of this code in the Sega FILM muxer behaves the same and
  
  has been treated the same.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/movenc.c
  • [DH] libavformat/segafilmenc.c

• VLC - Transcoding a 4k Picture to a Transport Stream

  20 janvier 2020, par gdogg371

  After a lot of crying, stamping my feet and pulling my hair out, I have now managed to transcode my 4k capture card into an RTP MPEG2 transport stream using VLC, as per the below :

  vlc dshow:// :dshow-vdev="Video (00 Pro Capture HDMI 4K+)" :dshow-adev="Audio (2- 00 Pro Capture HDMI 4K+)" :dshow-threads=8 :dshow-aspect-ratio=16\:9 :dshow-size="2160x1080" :dshow-pixel_format=NV12 :dshow-tune=film :dshow-preset=veryslow :dshow-vcodec=hevc_nvenc :dshow-fps=50 :dshow-crf=0 :dshow-acodec=mp4a :dshow-stereo-mode=5 :dshow-force-surround-sound=0 :dshow-ab=128 :dshow-samplerate=44100 :no-dshow-config :live-caching=100 :sout=#transcode{venc=ffmpeg,vcodec=mp2v,threads=8,aspect=16:9,width=2160,height=1080,fps=50,aenc=ffmpeg,acodec=a52,ab=1500,channels=6,samplerate=48000,soverlay}:rtp{dst=192.168.1.15,port=8554,mux=ts}

  My remaining issue though is, that I cannot get a 4k picture to transcode cleanly. I get horrendous stutter of the picture if I try and 2160x1080 at 50 fps is the best I have been able to achieve.

  The Magewell 4k card I have been using runs natively at 3840x2160 at 50fps, outputting a raw video signal. Is there some kind of built in limitation of MPEG2 where it cannot handle a 4k signal that I am not aware of ?

  Can anyone suggests some amendments to the above, so as to process a 4k signal properly ?

  Thanks

• ffmpeg can't transcode DVD ac3 audio stream, but VLC can play it

  21 février 2020, par RalphORama

  I’m attempting to transcode a DVD to a single MKV file. I’ve had success in the past with other DVDs, but I’m running into an error I haven’t seen before.

  First I concatenate the VOB files I want to transcode :

  cat VTS_02_1.VOB VTS_02_2.VOB VTS_02_3.VOB > WMAV.VOB

  ffprobe output :

  $ ffprobe -analyzeduration 100M -probesize 100M WMAV.VOB                                                                         Input #0, mpeg, from 'WMAV.VOB':
  
    Duration: 01:05:19.42, start: 0.300300, bitrate: 5686 kb/s
  
      Stream #0:0[0x1bf]: Data: dvd_nav_packet
  
      Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, smpte170m, top first), 720x480 [SAR 32:27 DAR 16:9], 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
  
      Stream #0:2[0x80]: Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s
  
  Unsupported codec with id 100357 for input stream 0

  Then I run this command to transcode the file :

  ffmpeg -analyzeduration 100M -probesize 100M \
  
    -i WMAV.VOB \
  
    -map 0:1 -map 0:2 \
  
    -c:v libx264 -preset slow -tune film -crf 21 \
  
    -c:a aac -b:a 192k \
  
    wmav.mkv

  However, when I include -c:a aac, I get thousands of errors like this :

  Error while decoding stream #0:2: Error number -16976906 occurred
  
  [ac3 @ 000002bd24d8eec0] expacc 127 is out-of-range
  
  [ac3 @ 000002bd24d8eec0] error decoding the audio block

  There doesn’t seem to be any issue with the audio stream since it plays back fine in VLC. The transcode succeeds if I use -c:a copy.

  What is causing this error and how could I fix the problem ?