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• What is the ideal image format extraction for YUV color space and lossless compression from mxf video format using ffmpeg

  15 février 2016, par DragonDance27

  I would like to be able to work on frames from an .mxf video file. The image format of the video is JPEG 2000, using a YUV color space with 4:2:2 subsampling and lossless compression.

  My intentions are to extract frames from this video using ffmpeg. Extracted frames would then be processed in Matlab (at the moment I’m interested in performing colorization).

  I want to extract the frames with as minimal data loss as possible and I would like to work in the YUV color space. I understand PNG involves a lossless process, but only involves the RGB color space - so not an option.

  I think I can extract jpeg2000 frames in the YUV color space, but I’m not sure if I’m losing data from the compression process. I attempted the following code in ffmpeg :

  ffmpeg -i video.mxf -r 1/5 out%03d.jp2

  ... however, the extracted jp2 files are unreadable in various software, including HiView which is a specialised JPEG 2000 software.

  Quesiton 1 : Is this jpeg 2000 extraction method lossless ? What am I doing wrong ?

  I also considered extracting the images in the tiff format where I can achieve the YUV and lossless requirements. I attempted the following code in ffmpeg :

  ffmpeg -i video.mxf -vcodec tiff f%10d.tif

  ... however, the extracted tiff files are unreadable in software such as paint, paint.net and windows photo viewer.

  Question 2 : Is this tiff extraction method correct ? What am I doing wrong ?

  Question 3 : What is an ideal image format that covers my YUV and lossless requirements ?

• How to raw TS packets off a file/url — Without decoding

  15 août 2019, par Znura

  New to ffmpeg and playing around that to understand better. I’m trying to use ffmpeg code base to get TS packets from a HLS Streaming server. I don’t need any decoding as I just have to store the TS packets to be processed later.

  First I built a minimal FFMPEG as outlined in https://zeranoe.com/forum/viewtopic.php?f=5&t=7426. No decoders and only hls and mpegts demuxers. Then using the following code to receive the frames. While inspecting it doesn’t seem to be MPEG-TS packets while looking into buffers thru GDB. Attaching the code here..

  Two Questions :

  1. Shouldn’t the av_recv_frame get me the TS packets ? However When I trace all the way to playlists (off HLSContext), the read_buffer there contains TS packets. IS there any example I could look into to get TS packets in this scenario without decoders ?

  2. If I get answer for (1), How to get the best stream off the HLS server ? when looking into ffplay, av_find_best_stream() sounds like the one to look into.. But again without needing to decode, is there a way to get best one according to the network condition ?

  Thanks..

  I dumped whatever I got off av_recv_frame() and stored in file. This file is not playable with VLC but Windows Movies & TV player could play the sound with missing frames..

  int main(int argc, char *argv[]) { 
  
      AVFormatContext * ifmt_ctx = NULL; 
  
      char *in_filename = NULL; 
  
      int ret = 0; 
  
      AVPacket pkt; 
  
      if (argc != 2) { return 1; } 
  
      in_filename = argv[1]; 
  
      av_register_all();
  
  
  
      if (!(ifmt_ctx = avformat_alloc_context())) { goto end; } 
  
      if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) { 
  
          fprintf(stderr, "Could not open input file '%s'", in_filename); 
  
          goto end; 
  
      } 
  
      if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) { 
  
          fprintf(stderr, "Failed to retrieve input stream information"); 
  
          goto end; 
  
      }
  
  
  
      av_dump_format(ifmt_ctx, 0, in_filename, 0); 
  
      while (1) { 
  
          ret = av_read_frame(ifmt_ctx, &pkt); 
  
          if (ret < 0) break; 
  
          av_free_packet(&pkt); 
  
      } 
  
      end: avformat_close_input(&ifmt_ctx); return 0; 
  
  } 

• lavc/opusdsp : rewrite R-V V postfilter

  2 novembre 2023, par Rémi Denis-Courmont

  lavc/opusdsp : rewrite R-V V postfilter
  This uses a more traditional approach allowing up processing of up to
  
  period minus two elements per iteration. This also allows the algorithm
  
  to work for all and any vector length.
  As the T-Head C908 device under test can load 16 elements loop, there is
  
  unsurprisingly a little performance drop when the period is minimal and
  
  the parallelism is capped at 13 elements :
  Before :
  
  postfilter_15_c :         21222.2
  
  postfilter_15_rvv_f32 :   22007.7
  
  postfilter_512_c :        20189.7
  
  postfilter_512_rvv_f32 :  22004.2
  
  postfilter_1022_c :       20189.7
  
  postfilter_1022_rvv_f32 : 22004.2
  After :
  
  postfilter_15_c :         20189.5
  
  postfilter_15_rvv_f32 :    7057.2
  
  postfilter_512_c :        20189.5
  
  postfilter_512_rvv_f32 :   5667.2
  
  postfilter_1022_c :       20192.7
  
  postfilter_1022_rvv_f32 :  5667.2
  

  • [DH] libavcodec/riscv/opusdsp_init.c
  • [DH] libavcodec/riscv/opusdsp_rvv.S