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• I need some help accurately trimming video using the FFmpeg C api

  20 mars 2015, par Justin Bradley

  I need some help accurately trimming video using the FFmpeg C api.
  What I’m seeing is when the input video stream has a time_base of 1/48000 it correctly selects the trimmed start and end times. However when the input video stream has a time_base other than 1/48000 the trim is incorrect.

  Time bases of 1/30000 and 1/24000 trim half the expected video stream length - 10s instead of 20s.
  1/25 trims almost nothing at all - the output file size is only a few kb.

  The audio stream appears to always be trimmed correctly.

  For example if I try to trim the first 20s of a video whose video stream time base is 1/30000, the output mp4’s length is 20s. It has first 10s of video and first 20s of audio.

  I think I’m incorrectly calculating the end_time but I’m not sure why it’s correct for 1/48000 time_base streams.

  record[i].start_time = av_rescale_q((int64_t)( start_time * AV_TIME_BASE ), default_timebase, in_stream->time_base);
  
  record[i].end_time = av_rescale_q((int64_t)( end_time   * AV_TIME_BASE ), default_timebase, in_stream->time_base);

  Here is a more complete sample of code :

  int num_of_streams = ifmt_ctx->nb_streams;
  
  if(num_of_streams > 0) {
  
      // keeps track of each stream's trimmed start and end times
  
      struct stream_pts record[num_of_streams];
  
  
  
      for (i = 0; i < num_of_streams; i++) {
  
          AVStream *in_stream = ifmt_ctx->streams[i];
  
          AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
  
          if (!out_stream) {
  
              LOGE("=> Failed allocating output stream");
  
              ret = AVERROR_UNKNOWN;
  
              return close_connection(ret);
  
          }
  
  
  
          ret = avcodec_copy_context(out_stream->codec, in_stream->codec);
  
          if (ret < 0) {
  
              LOGE("=> Failed to copy context from input to output stream codec context");
  
              return close_connection(ret);
  
          }
  
          out_stream->codec->codec_tag = 0;
  
          if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
  
              out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
  
  
          AVRational default_timebase;
  
          default_timebase.num = 1;
  
          default_timebase.den = AV_TIME_BASE;
  
  
  
          // determine start/end times for each stream
  
          record[i].index = i;
  
          record[i].start_time = av_rescale_q((int64_t)( start_time * AV_TIME_BASE ), default_timebase, in_stream->time_base);
  
          record[i].end_time = av_rescale_q((int64_t)( end_time   * AV_TIME_BASE ), default_timebase, in_stream->time_base);
  
      }
  
  
  
      av_dump_format(ofmt_ctx, 0, output_file, 1);
  
  
  
      if (!(ofmt->flags & AVFMT_NOFILE)) {
  
          ret = avio_open(&ofmt_ctx->pb, output_file, AVIO_FLAG_WRITE);
  
          if (ret < 0) {
  
              LOGE("=> Could not open output file '%s'", output_file);
  
              return close_connection(ret);
  
          }
  
      }
  
  
  
      ret = avformat_write_header(ofmt_ctx, NULL);
  
      if (ret < 0) {
  
          LOGE("=> Error occurred when opening output file");
  
          return close_connection(ret);
  
      }
  
  
  
      while (1) {
  
          AVStream *in_stream, *out_stream;
  
  
  
          ret = av_read_frame(ifmt_ctx, &pkt);
  
          if (ret < 0)
  
              break;
  
  
  
          in_stream  = ifmt_ctx->streams[pkt.stream_index];
  
          out_stream = ofmt_ctx->streams[pkt.stream_index];
  
  
  
          // copy packet
  
          pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
  
          pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
  
          pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
  
          pkt.pos = -1;
  
  
  
          // write the frames we're looking for
  
          if(pkt.pts >= record[pkt.stream_index].start_time && pkt.pts <= record[pkt.stream_index].end_time) {
  
              ret = av_interleaved_write_frame(ofmt_ctx, &pkt);
  
              if (ret < 0) {
  
                  LOGE("=> Error muxing packet");
  
                  break;
  
              }
  
          }
  
  
  
          av_free_packet(&pkt);
  
      }
  
  }

• ffmpeg to split mp4 file into segments... after first segment, audio unsynced

  13 avril 2015, par bcsteeve

  I’ve used the ffmpeg command line shown in this question to split MKV files perfectly for a long time. Now i have some MP4 files that i’d like to split and at first it seemed to work, but every subsequent segment after the first has the audio not synced ! And by several seconds.

  I’ve tried forcing keyframes (advice I found on some other sites) and that didn’t help.

  I tried a different program entirely (Avidemux) and it was able to split the file with proper output, but it was a LOT slower, taking upwards of 3 minutes vs less than 2 seconds with ffmpeg. With Avidemux I was able to determine the exact position of the i-frame where I wanted to split, so thinking perhaps that was the syncing problem I tried that exact position (ie. 00:12:17.111 instead of 00:12:16 or whatever) but that didn’t help either.

  Is there an option I’m missing with ffmpeg to get it to properly sync audio to the video when splitting ?

• ffmpeg runs in terminal but returns error in subprocess.run from flatpak-installed pycharm

  19 juin 2024, par name

  I want to run this command in python :

  


  ffmpeg -ss 00:00:30 -i "/home/exl/—1—ARCHIVE—1—/video/music videos/author --- a2 - name (text).webm" -vf scale=150:-2 -vframes 1 -c:v libwebp -compression_level 6 -quality 100 /home/exl/—1—ARCHIVE—1—/—3—previews—3—/734a8a0bac3a83e0f6c69416a26ec5cd211a6d742f3df63bb72bdbe6431b57c30677bc11551ba4aaaecac15ed2c48de51340a09020b7e9d9479e1e81ff766191.webp


  


  In terminal it works fine, but in subprocess returns error. Python code :

  


  finished_process = subprocess.run(
                    [
                        '/usr/bin/ffmpeg',
                        '-ss', f'00:00:{seconds_shift}',
                        '-i', original_path,
                        '-vf', 'scale=150:-2',
                        '-vframes', '1',
                        '-c:v', 'libwebp',
                        '-compression_level', '6',
                        '-quality', '100',
                        preview_path
                    ],
                    #stdout=subprocess.DEVNULL,
                    #stderr=subprocess.DEVNULL,
                    check=False,
                    capture_output=True
                )


  


  finished_process.stderr.decode() :

  


  ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 12.1.0 (GCC)
  configuration: --prefix=/usr --libdir=/usr/lib/x86_64-linux-gnu --disable-debug --disable-doc --disable-static --enable-optimizations --enable-shared --disable-everything --enable-ffplay --enable-ffprobe --enable-gnutls --enable-libaom --enable-libdav1d --enable-libfdk-aac --enable-libmp3lame --enable-libfontconfig --enable-libfreetype --enable-libopus --enable-libpulse --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libwebp --enable-openal --enable-opengl --enable-sdl2 --enable-vulkan --enable-zlib --enable-libv4l2 --enable-libxcb --enable-vdpau --enable-vaapi --enable-encoder='ac3,alac,flac,libfdk_aac,g723_1,mp2,libmp3lame,libopus,libspeex,pcm_alaw,pcm_mulaw,pcm_f32le,pcm_s16be,pcm_s24be,pcm_s16le,pcm_s24le,pcm_s32le,pcm_u8,tta,libvorbis,wavpack,' --enable-encoder='ass,ffv1,libaom_av1,libvpx_vp8,libvpx_vp9,mjpeg_vaapi,rawvideo,theora,vp8_vaapi,libopenh264' --enable-decoder='adpcm_g722,alac,flac,g723_1,g729,libfdk_aac,libopus,libspeex,mp2,mp3,m4a,pcm_alaw,pcm_mulaw,pcm_f16le,pcm_f24le,pcm_f32be,pcm_f32le,pcm_f64be,pcm_f64le,pcm_s16be,pcm_s16be_planar,pcm_s24be,pcm_s16le,pcm_s16le_planar,pcm_s24le,pcm_s24le_planar,pcm_s32le,pcm_s32le_planar,pcm_s64be,pcm_s64le,pcm_s8,pcm_s8_planar,pcm_u8,pcm_u24be,pcm_u24le,pcm_u32be,pcm_u32le,tta,vorbis,wavpack,' --enable-decoder='ass,ffv1,mjpeg,mjpegb,libaom_av1,libdav1d,libvpx_vp8,libvpx_vp9,rawvideo,theora,vp8,vp9,libopenh264' --enable-encoder='bmp,gif,jpegls,png,tiff,webp,' --enable-decoder='bmp,gif,jpegls,png,tiff,webp,' --enable-hwaccel='vp8_vaapi,mjpeg_vaapi,' --enable-parser='aac,ac3,flac,mjpeg,mpegaudio,mpeg4video,opus,vp3,vp8,vp9,vorbis,' --enable-muxer='ac3,ass,flac,g722,gif,matroska,mp3,mpegvideo,rtp,ogg,opus,pcm_s16be,pcm_s16le,wav,webm,' --enable-demuxer='aac,ac3,ass,flac,g722,gif,image_jpeg_pipe,image_png_pipe,image_webp_pipe,matroska,mjpeg,mov,mp3,mpegvideo,ogg,pcm_mulaw,pcm_alaw,pcm_s16be,pcm_s16le,rtp,wav,' --enable-filter='crop,scale,overlay,amix,amerge,aresample,format,aformat,fps,transpose,pad,' --enable-indev='v4l2,xcbgrab,' --enable-protocol='crypto,file,pipe,rtp,srtp,rtsp,tcp,udp,unix,' --arch=x86_64 --enable-libopenh264
  libavutil      57. 17.100 / 57. 17.100
  libavcodec     59. 18.100 / 59. 18.100
  libavformat    59. 16.100 / 59. 16.100
  libavdevice    59.  4.100 / 59.  4.100
  libavfilter     8. 24.100 /  8. 24.100
  libswscale      6.  4.100 /  6.  4.100
  libswresample   4.  3.100 /  4.  3.100
Input #0, matroska,webm, from '/home/exl/—1—ARCHIVE—1—/video/music videos/author --- a2 - name (text).webm':
  Metadata:
    ENCODER         : Lavf59.16.100
  Duration: 00:03:24.98, start: -0.007000, bitrate: 915 kb/s
  Stream #0:0(eng): Video: vp9 (Profile 0), yuv420p(tv, bt709), 1920x1036, SAR 1:1 DAR 480:259, 25 fps, 25 tbr, 1k tbn (default)
    Metadata:
      DURATION        : 00:03:24.960000000
  Stream #0:1(eng): Audio: opus, 48000 Hz, stereo, s16 (default)
    Metadata:
      DURATION        : 00:03:24.981000000
[NULL @ 0x55dd82de7d00] Unable to find a suitable output format for '/home/exl/—1—ARCHIVE—1—/—3—previews—3—/734a8a0bac3a83e0f6c69416a26ec5cd211a6d742f3df63bb72bdbe6431b57c30677bc11551ba4aaaecac15ed2c48de51340a09020b7e9d9479e1e81ff766191.webp'
/home/exl/—1—ARCHIVE—1—/—3—previews—3—/734a8a0bac3a83e0f6c69416a26ec5cd211a6d742f3df63bb72bdbe6431b57c30677bc11551ba4aaaecac15ed2c48de51340a09020b7e9d9479e1e81ff766191.webp: Invalid argument



  


  As suggested here (FFMPEG command runs in terminal but not by subprocess) i tried using which determine path to correct version, but this command returns /usr/bin/ffmpeg both in python and in terminal.

  


  which ffmpeg (both subprocess.run(['which', 'ffmpeg'], capture_output=True).stdout and terminal) : /usr/bin/ffmpeg

  


  ffmpeg -version : 5.1.1-1ubuntu1

  


  ffmpeg version 5.1.1-1ubuntu1 Copyright (c) 2000-2022 the FFmpeg developers
built with gcc 12 (Ubuntu 12.2.0-1ubuntu1)
configuration: --prefix=/usr --extra-version=1ubuntu1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libglslang --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librist --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --disable-sndio --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-libplacebo --enable-shared


  


  subprocess.run(['ffmpeg', '-version'], capture_output=True).stdout.decode() : 5.0.1

  


  ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
built with gcc 12.1.0 (GCC)
configuration: --prefix=/usr --libdir=/usr/lib/x86_64-linux-gnu --disable-debug --disable-doc --disable-static --enable-optimizations --enable-shared --disable-everything --enable-ffplay --enable-ffprobe --enable-gnutls --enable-libaom --enable-libdav1d --enable-libfdk-aac --enable-libmp3lame --enable-libfontconfig --enable-libfreetype --enable-libopus --enable-libpulse --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libwebp --enable-openal --enable-opengl --enable-sdl2 --enable-vulkan --enable-zlib --enable-libv4l2 --enable-libxcb --enable-vdpau --enable-vaapi --enable-encoder='ac3,alac,flac,libfdk_aac,g723_1,mp2,libmp3lame,libopus,libspeex,pcm_alaw,pcm_mulaw,pcm_f32le,pcm_s16be,pcm_s24be,pcm_s16le,pcm_s24le,pcm_s32le,pcm_u8,tta,libvorbis,wavpack,' --enable-encoder='ass,ffv1,libaom_av1,libvpx_vp8,libvpx_vp9,mjpeg_vaapi,rawvideo,theora,vp8_vaapi,libopenh264' --enable-decoder='adpcm_g722,alac,flac,g723_1,g729,libfdk_aac,libopus,libspeex,mp2,mp3,m4a,pcm_alaw,pcm_mulaw,pcm_f16le,pcm_f24le,pcm_f32be,pcm_f32le,pcm_f64be,pcm_f64le,pcm_s16be,pcm_s16be_planar,pcm_s24be,pcm_s16le,pcm_s16le_planar,pcm_s24le,pcm_s24le_planar,pcm_s32le,pcm_s32le_planar,pcm_s64be,pcm_s64le,pcm_s8,pcm_s8_planar,pcm_u8,pcm_u24be,pcm_u24le,pcm_u32be,pcm_u32le,tta,vorbis,wavpack,' --enable-decoder='ass,ffv1,mjpeg,mjpegb,libaom_av1,libdav1d,libvpx_vp8,libvpx_vp9,rawvideo,theora,vp8,vp9,libopenh264' --enable-encoder='bmp,gif,jpegls,png,tiff,webp,' --enable-decoder='bmp,gif,jpegls,png,tiff,webp,' --enable-hwaccel='vp8_vaapi,mjpeg_vaapi,' --enable-parser='aac,ac3,flac,mjpeg,mpegaudio,mpeg4video,opus,vp3,vp8,vp9,vorbis,' --enable-muxer='ac3,ass,flac,g722,gif,matroska,mp3,mpegvideo,rtp,ogg,opus,pcm_s16be,pcm_s16le,wav,webm,' --enable-demuxer='aac,ac3,ass,flac,g722,gif,image_jpeg_pipe,image_png_pipe,image_webp_pipe,matroska,mjpeg,mov,mp3,mpegvideo,ogg,pcm_mulaw,pcm_alaw,pcm_s16be,pcm_s16le,rtp,wav,' --enable-filter='crop,scale,overlay,amix,amerge,aresample,format,aformat,fps,transpose,pad,' --enable-indev='v4l2,xcbgrab,' --enable-protocol='crypto,file,pipe,rtp,srtp,rtsp,tcp,udp,unix,' --arch=x86_64 --enable-libopenh264


  


  Thank you in advance.