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• How to reliably probe a VOB for the aspect ratio of a DVD ?

  2 mars 2015, par IAmDamoSuzuki

  I’m building an automation system for ingesting and transcoding DVDs, but am running into some trouble with aspect ratios. I’m able to detect the aspect ration of a VOB with the following command :

  mediaInfoOutput -f [input file] | grep "Display aspect ratio" | awk '{print $5}'

  This works most of the time, however there are a few cases where the content is shot in 16:9, but the VOB reports itself as 4:3. What’s stranger is that Apple DVD Player plays the DVD back (when the ISO mounted) as 16:9. This makes me think that the DVD Player application is looking at some metadata field other than "Display Aspect Ratio" for the VOB itself.

  One possible clue is that the menus for these DVDs tend to be 4:3, while the content is 16:9. However, my code makes sure to only look at the DAR of the first non-menu VOB.

  What’s going on here ? How can I reliably find the aspect ratio of DVD content ?

• Change the Sample/Pixel aspect ratio of video with least possible video re-encoding

  27 août 2022, par PiTao

  I need to have some mp4 videos with square sample (pixel) aspect ratio (1:1) i.e. square pixels. However, as ffprobe shows my video has PAR of 59:54.

  


  I have tried using this command :

  


  ffmpeg  -i in.mp4 -c copy -bsf:v "h264_metadata=sample_aspect_ratio=1/1" out.mp4


  


  but still the PAR has not changed in my downstream applicaiton or as I checked it with the ffprobe :

  


  ffprobe version n5.1 Copyright (c) 2007-2022 the FFmpeg developers
  built with gcc 12.1.1 (GCC) 20220730
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-amf --enable-avisynth --enable-cuda-llvm --enable-lto --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libdav1d --enable-libdrm --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libjack --enable-libmfx --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librav1e --enable-librsvg --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxml2 --enable-libxvid --enable-libzimg --enable-nvdec --enable-nvenc --enable-shared --enable-version3
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'vimeo_11261121.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf59.27.100
  Duration: 00:00:52.36, start: 0.000000, bitrate: 519 kb/s
  Stream #0:0[0x1](eng): Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), yuv444p(progressive), 720x576 [SAR 1:1 DAR 5:4], 382 kb/s, SAR 59:54 DAR 295:216, 25 fps, 25 tbr, 12800 tbn (default)
    Metadata:
      handler_name    : Apple Video Media Handler
      vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 130 kb/s (default)
    Metadata:
      handler_name    : Apple Sound Media Handler
      vendor_id       : [0][0][0][0]


  


  If I not mistaken, the ffmpeg only changes the metadata and not the actual PAR. Is it possible to change the PAR (sample aspect ratio) preferably without much re-encoding ?

  


• Some Queries on HLS Independent Segments and AAC codec ?

  1er mars 2023, par muraliv

  According to Apple HLS spec, #EXT-X-INDEPENDENT-SEGMENTS tag indicates that the segments are independent and can be decoded indepedently of each other. This tag can be specified either in master playlist or rendition playlist or both.

  


  I assume that this applies for both video and audio decoding ? If so, if I used MediaConvert or ffmpeg to prepare a HLS stream with AAC-LC codec, then audio for each HLS segements can be decoded independently ? I read somewhere that AAC requires 2 packets/frames for decoding due to its overlapping encoding logic. Then, will the first audio packet for the next HLS segment depend on the last audio packet of the previous HLS segment for decoding, or is it still the case that the audio packets can be decoded independently across HLS segments ?