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• ffmpeg change video stream resolution

  10 décembre 2014, par skorpionet

  I have an MKV with a video stream with wrong resolution of 1920x800, but the inside film is 1920x1080 so my main video player, an LG Smart TV, shows a flattened image. I can easily change resolution in container metadata but LG TV ignores this data and read only video stream data.

  First question : only way to change video stream resolution data is scale the video ?

  To scale with ffmpeg I used this command :

  ffmpeg -i input.mkv -map 0 -c:a copy -c:s copy -c:v libx264 -preset slow -crf 17 -vf scale=1920:1080,setdar=16/9 output.mkv

  Now the mkv is fine, my LG TV read it, looks awesome but..... size went from 3,3Gb to 12Gb !!
  Overall bit rate of 3,3Gb video is 2.704 Kbps, 12Gb is 9.829 Kbps. I think that 7000Kbps more are useless, in original video there aren’t info to raise quality.

  Second question : Why this huge size change ? What is my mistake ?

  Best Regards

• FFMPEG Windows Batch - Recursive Convert based and settings based on Frame Height

  3 avril 2017, par Vahid Jamali

  So I’m trying to make a batch file to use FFMPEG to convert around 1000 MP4 video files.

  I want to recursively go through these folders, possibly use ffprobe to discover the frame height, and then based on the frame height options (360, 480, 720, or 1080 frame height) give them individually different ffmpeg commands.

  I’ve been reading up on various approaches to this just as far as batch processing goes.

  So far I’m at this stage :

  for %%a in ("*.*") do C:\ffinstall\local64\bin-video\ffmpeg -i "%%a"  -c:v libx264 -crf 18 -preset veryslow -tune film -refs 8 -bf 6 -aq-mode 2 -filter_complex "[0:v][1:v]overlay=30:main_h-overlay_h-30,subtitles='D:\add.ass'" -c:a copy "encoded\%%~na.mp4"

  pause

  Code to discover the frame height :

  ffprobe -v error -show_entries stream=height -of default=noprint_wrappers=1 inputfile.mp4

  Trying to figure out conditionals and how their syntax is. Also I’m getting a Unable to parse option value "add.ass" as image size error. Which I believe is due to not being to see the subtitle file.

  Any suggestions on where I can start ? Thanks for any help.

• FFMPEG : Video decoder integration giving segmentation fault

  5 décembre 2013, par Zax

  I have integrated a decoder to FFMPEG multimedia framework. I have referred this how to post to integrate the decoder.

  How to integrate a codec to FFMPEG

  I have followed the above post and integrated my custom decoder which decodes an elementary stream into a YUV420 data.

  However, When i give an input command as shown below, i get the following messages in sequence :

  ./ffmpeg -vcodec myCustomDec -i input_416x240.bin opt.yuv

  For integrating a codec, we need to define 3 functions and assign them to AVCodec's structures function pointers .init, .close and .decode.

  I have given a printf statement in myCustomDec's demuxer's probe function, init function, decode function and close function.

  The output i get after executing the above command is :

  myCustomDecoder probe function Entered
  
  myCustomDecoder demux successful
  
  Codec 0x73736d77 is not in the full list.
  
  Init is Entered
  
   Last message repeated 1 times
  
  Decode entered
  
  Segmentation fault (core dumped)

  So, this means that i'm getting segmentation fault after after entering decode function. My decode function prototype is as shown below :

  static int myCustom_decode_frame(AVCodecContext *avctx, void *data,int *got_frame_ptr, AVPacket *avpkt)

  In this function what i actually do is :

  AVFrame *frame     = data;
  
  printf("\nDecode entered\n");
  
  //Here i call decode frame function
  
  
  
  //Here i call a function to fetch YUV data
  
  
  
  //now i make the pointer that is pointing to YUV buffer data to point to variable of type AVFrame *frame
  
  
  
  //set *got_frame to 1

  So my expectation here is that once i map my YUV buffer pointer to the AVFrame *frame variable, the FFMPEG multimedia framework will take care of dumping this yuv frame to opt.yuv which is specified in the command. My question is : Is my assumption correct that FFMPEG multimedia frame work takes care of dumping data to output file ?

  Second, Why am i getting a message in the output saying Codec 0x73736d77 is not in the full list.

  And finally, How does the FFMPEG framework get to know the width and height of the input stream that i'm providing, because my parser is embeded in the decode code itself, and there is no connection with FFMPEG.

  Any suggestion regarding the same will be really helpful to me. Please do provide your suggestions. Thanks in advance.