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• HEVC : Fetching the input width and height from input bin stream

  1er juillet 2022, par Zax

  I have created an elementary bin stream using HM-12.0 reference code. So the out put is an HEVC encoded bin stream (say input.bin).

  



  I have a task which involves reading the header of this elementary stream. That is i need to fetch information such a the stream width, height etc. from the input.bin file.

  



  After seeing a lots of streams, i can conclude that all these bin streams starts from the sequence :

  



  00 00 00 01


  



  So whenever i see this sequence in any bin stream, i can say that this stream has to be decoded by HEVC decoder.

  



  Further if i want to fetch the width, height, fps etc. from the input.bin (like ff_raw_video_read_header function in ffmpeg), that are the steps need to be performed to fetch this information ?

  



  I have gone through the parsing section of the HEVC draft, but its very complicated for my level in video domain. Can anyone suggest a simple way to fetch the required information from the encoded bin file ?

  



  Any suggestions will be really helpful to me. Thanks in advance.

  


• FFMEPG crop : Invalid too big or non positive size for width '1920' or height '1040'

  12 février 2021, par NatePhysics

  I run into a strange issue with a particular file in FFMPEG. When I try and crop it down a little I get :

  


  [Parsed_crop_0 @ 000002ad60c27980] Invalid too big or non positive size for width '1920' or height '1040'
[Parsed_crop_0 @ 000002ad60c27980] Failed to configure input pad on Parsed_crop_0
Error reinitializing filters!
Failed to inject frame into filter network: Invalid argument
Error while processing the decoded data for stream #0:37
Conversion failed!


  


  This is odd to me because you can even see from the stream metadata that the resolution is much higher :

  


  Metadata:
    encoder         : libebml v1.4.0 + libmatroska v1.6.2
    creation_time   : 2021-02-09T22:45:47.000000Z
  Duration: 02:17:48.93, start: 0.000000, bitrate: 8548 kb/s
    Stream #0:0: Video: h264 (High), yuv420p(progressive), **1920x1080** [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)


  


  There's only 1 video stream. I'm running the following command :

  


  ffmpeg -i "wedding.mkv" -filter:v "crop=1920:1040" -c:v libx264 -preset slow -tune film -profile:v high -level 4.1 -crf 19 -c:a copy -c:s copy -map 0 "wedding-cropped.mkv"


  


  I can preview the crop using the following command without any errors :

  


  ffplay -i "wedding.mkv" -vf "crop=1920:960"


  


  I've cropped a few files before without issue. I'm a bit confused as to why I'm getting a resolution error in this case when the video file is clearly higher resolution. I've also tested lowering the cropped resolution and even when I lower both by several hundred pixels it still spits out the same error. Any thoughts or suggestions ?

  


• FFMpeg : scale down videos with maximum width and height while maintaining aspect ratio

  20 février 2021, par R3D34THR4Y

  In my program the user can input any video file he wants and have it transcoded ready for social media no matter its dimensions and aspect ratio.
The "export profiles" have many variables but the important ones here are maxheight and maxwidth.

  


  The FFMpeg filters must output a video that follows the following rules :

  


  

  • If the video is vertical, permutate the maxheight and maxwidth values (social media considers both 1280x720 and 720x1280 as "720P")

  


  • The video must not have a height superior to maxheight or a width superior to maxwidth.

  


  • The original video and exported video have the same aspect ratio and no distortion occurs.

  


  • No padding or cropping should occur.

  


  • The video should not be scaled if it is already under those maximum dimensions (no upscaling).

  


  • The function must work even with odd input resolutions.

  


  


  I have tried finding a combination of filters that do that but I haven't been able so far, either the video gets distorted or it gets huge black bars if the aspect ratio isn't right, the solution may be simple but I'm a beginner on this library so I'm probably just missing an easy solution.

  


  My current solution :

  


  ffmpeg -i input.mp4 -vf [in] scale=1280:720:flags=lanczos:force_original_aspect_ratio=decrease,pad=1280:720:(ow-iw)/2:(oh-ih)/2,setsar=1 [res]; [res] format=yuv420p [format] -c:v libx264 -c:a aac -movflags +faststart output.mp4


  


  Thanks for reading