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• How to keep transparency when scale webm file with ffmpeg

  5 octobre 2022, par Sonia Kidman

  I'm using ffmpeg to scale my WEBM file, by using below command : 
ffmpeg -i in.webm -c:v libvpx -vf scale=100:100 out.webm
The output has correct resolution as I expected but the problem is transparency become black background.

  



  Could someone give me a solution for this.

  



  Thank you so much.

  



  Below is the log of the operation :

  



  ffmpeg version 3.4 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 7.2.0 (GCC)
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-bzlib --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-cuda --enable-cuvid --enable-d3d11va --enable-nvenc --enable-dxva2 --enable-avisynth --enable-libmfx
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Splitting the commandline.
Reading option '-v' ... matched as option 'v' (set logging level) with argument '56'.
Reading option '-i' ... matched as input url with argument 'in.webm'.
Reading option '-c:v' ... matched as option 'c' (codec name) with argument 'libvpx'.
Reading option '-vf' ... matched as option 'vf' (set video filters) with argument 'scale=320:240'.
Reading option 'out.webm' ... matched as output url.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option v (set logging level) with argument 56.
Successfully parsed a group of options.
Parsing a group of options: input url in.webm.
Successfully parsed a group of options.
Opening an input file: in.webm.
[NULL @ 000002387e6322a0] Opening 'in.webm' for reading
[file @ 000002387e632ea0] Setting default whitelist 'file,crypto'
Probing matroska,webm score:100 size:2048
Probing mp3 score:1 size:2048
[matroska,webm @ 000002387e6322a0] Format matroska,webm probed with size=2048 and score=100
st:0 removing common factor 1000000 from timebase
[matroska,webm @ 000002387e6322a0] Before avformat_find_stream_info() pos: 634 bytes read:32768 seeks:0 nb_streams:1
[matroska,webm @ 000002387e6322a0] All info found
[matroska,webm @ 000002387e6322a0] stream 0: start_time: 0.000 duration: -9223372036854776.000
[matroska,webm @ 000002387e6322a0] format: start_time: 0.000 duration: 0.400 bitrate=1432 kb/s
[matroska,webm @ 000002387e6322a0] After avformat_find_stream_info() pos: 34843 bytes read:65536 seeks:0 frames:1
Input #0, matroska,webm, from 'in.webm':
  Metadata:
    ENCODER         : Lavf57.83.100
  Duration: 00:00:00.40, start: 0.000000, bitrate: 1432 kb/s
    Stream #0:0, 1, 1/1000: Video: vp8, 1 reference frame, yuv420p(progressive), 640x480, 0/1, SAR 1:1 DAR 4:3, 10 fps, 10 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      alpha_mode      : 1
      ENCODER         : Lavc57.107.100 libvpx
      DURATION        : 00:00:00.400000000
Successfully opened the file.
Parsing a group of options: output url out.webm.
Applying option c:v (codec name) with argument libvpx.
Applying option vf (set video filters) with argument scale=320:240.
Successfully parsed a group of options.
Opening an output file: out.webm.
[file @ 000002387e658b40] Setting default whitelist 'file,crypto'
Successfully opened the file.
detected 4 logical cores
Stream mapping:
  Stream #0:0 -> #0:0 (vp8 (native) -> vp8 (libvpx))
Press [q] to stop, [?] for help
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
    Last message repeated 4 times
[Parsed_scale_0 @ 000002387e718a60] Setting 'w' to value '320'
[Parsed_scale_0 @ 000002387e718a60] Setting 'h' to value '240'
[Parsed_scale_0 @ 000002387e718a60] Setting 'flags' to value 'bicubic'
[Parsed_scale_0 @ 000002387e718a60] w:320 h:240 flags:'bicubic' interl:0
[graph 0 input from stream 0:0 @ 000002387e743b00] Setting 'video_size' to value '640x480'
[graph 0 input from stream 0:0 @ 000002387e743b00] Setting 'pix_fmt' to value '0'
[graph 0 input from stream 0:0 @ 000002387e743b00] Setting 'time_base' to value '1/1000'
[graph 0 input from stream 0:0 @ 000002387e743b00] Setting 'pixel_aspect' to value '1/1'
[graph 0 input from stream 0:0 @ 000002387e743b00] Setting 'sws_param' to value 'flags=2'
[graph 0 input from stream 0:0 @ 000002387e743b00] Setting 'frame_rate' to value '10/1'
[graph 0 input from stream 0:0 @ 000002387e743b00] w:640 h:480 pixfmt:yuv420p tb:1/1000 fr:10/1 sar:1/1 sws_param:flags=2
[format @ 000002387e7fe1e0] compat: called with args=[yuv420p|yuva420p]
[format @ 000002387e7fe1e0] Setting 'pix_fmts' to value 'yuv420p|yuva420p'
[AVFilterGraph @ 000002387e634e60] query_formats: 4 queried, 3 merged, 0 already done, 0 delayed
[Parsed_scale_0 @ 000002387e718a60] w:640 h:480 fmt:yuv420p sar:1/1 -> w:320 h:240 fmt:yuv420p sar:1/1 flags:0x4
[libvpx @ 000002387e657fe0] v1.6.1
[libvpx @ 000002387e657fe0] --prefix=/Users/kyle/software/libvpx/win64/libvpx-1.6.1-win64 --target=x86_64-win64-gcc
[libvpx @ 000002387e657fe0] vpx_codec_enc_cfg
[libvpx @ 000002387e657fe0] generic settings
  g_usage:                      0
  g_threads:                    0
  g_profile:                    0
  g_w:                          320
  g_h:                          240
  g_bit_depth:                  8
  g_input_bit_depth:            8
  g_timebase:                   {1/30}
  g_error_resilient:            0
  g_pass:                       0
  g_lag_in_frames:              0
[libvpx @ 000002387e657fe0] rate control settings
  rc_dropframe_thresh:          0
  rc_resize_allowed:            0
  rc_resize_up_thresh:          60
  rc_resize_down_thresh:        30
  rc_end_usage:                 0
  rc_twopass_stats_in:          0000000000000000(0)
  rc_target_bitrate:            256
[libvpx @ 000002387e657fe0] quantizer settings
  rc_min_quantizer:             4
  rc_max_quantizer:             63
[libvpx @ 000002387e657fe0] bitrate tolerance
  rc_undershoot_pct:            100
  rc_overshoot_pct:             100
[libvpx @ 000002387e657fe0] decoder buffer model
  rc_buf_sz:                    6000
  rc_buf_initial_sz:            4000
  rc_buf_optimal_sz:            5000
[libvpx @ 000002387e657fe0] 2 pass rate control settings
  rc_2pass_vbr_bias_pct:        50
  rc_2pass_vbr_minsection_pct:  0
  rc_2pass_vbr_maxsection_pct:  400
[libvpx @ 000002387e657fe0] keyframing settings
  kf_mode:                      1
  kf_min_dist:                  0
  kf_max_dist:                  128
[libvpx @ 000002387e657fe0] 
[libvpx @ 000002387e657fe0] vpx_codec_enc_cfg
[libvpx @ 000002387e657fe0] generic settings
  g_usage:                      0
  g_threads:                    0
  g_profile:                    0
  g_w:                          320
  g_h:                          240
  g_bit_depth:                  8
  g_input_bit_depth:            8
  g_timebase:                   {1/10}
  g_error_resilient:            0
  g_pass:                       0
  g_lag_in_frames:              25
[libvpx @ 000002387e657fe0] rate control settings
  rc_dropframe_thresh:          0
  rc_resize_allowed:            0
  rc_resize_up_thresh:          60
  rc_resize_down_thresh:        30
  rc_end_usage:                 0
  rc_twopass_stats_in:          0000000000000000(0)
  rc_target_bitrate:            200
[libvpx @ 000002387e657fe0] quantizer settings
  rc_min_quantizer:             4
  rc_max_quantizer:             63
[libvpx @ 000002387e657fe0] bitrate tolerance
  rc_undershoot_pct:            100
  rc_overshoot_pct:             100
[libvpx @ 000002387e657fe0] decoder buffer model
  rc_buf_sz:                    6000
  rc_buf_initial_sz:            4000
  rc_buf_optimal_sz:            5000
[libvpx @ 000002387e657fe0] 2 pass rate control settings
  rc_2pass_vbr_bias_pct:        50
  rc_2pass_vbr_minsection_pct:  0
  rc_2pass_vbr_maxsection_pct:  400
[libvpx @ 000002387e657fe0] keyframing settings
  kf_mode:                      1
  kf_min_dist:                  0
  kf_max_dist:                  128
[libvpx @ 000002387e657fe0] 
[libvpx @ 000002387e657fe0] vpx_codec_control
[libvpx @ 000002387e657fe0]   VP8E_SET_CPUUSED:             1
[libvpx @ 000002387e657fe0]   VP8E_SET_ARNR_MAXFRAMES:      0
[libvpx @ 000002387e657fe0]   VP8E_SET_ARNR_STRENGTH:       3
[libvpx @ 000002387e657fe0]   VP8E_SET_ARNR_TYPE:           3
[libvpx @ 000002387e657fe0]   VP8E_SET_NOISE_SENSITIVITY:   0
[libvpx @ 000002387e657fe0]   VP8E_SET_TOKEN_PARTITIONS:    0
[libvpx @ 000002387e657fe0]   VP8E_SET_STATIC_THRESHOLD:    0
[libvpx @ 000002387e657fe0] Using deadline: 1000000
Output #0, webm, to 'out.webm':
  Metadata:
    encoder         : Lavf57.83.100
    Stream #0:0, 0, 1/1000: Video: vp8 (libvpx), 1 reference frame, yuv420p, 320x240 [SAR 1:1 DAR 4:3], 0/1, q=-1--1, 200 kb/s, 10 fps, 1k tbn, 10 tbc (default)
    Metadata:
      alpha_mode      : 1
      DURATION        : 00:00:00.400000000
      encoder         : Lavc57.107.100 libvpx
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
Clipping frame in rate conversion by 0.000008
[webm @ 000002387e656880] get_metadata_duration returned: 400000
[webm @ 000002387e656880] Write early duration from metadata = 400
[webm @ 000002387e656880] Writing block at offset 3, size 11223, pts 0, dts 0, duration 100, keyframe 1
[webm @ 000002387e656880] Writing block at offset 11233, size 1288, pts 100, dts 100, duration 100, keyframe 0
[webm @ 000002387e656880] Writing block at offset 12528, size 1504, pts 200, dts 200, duration 100, keyframe 0
[webm @ 000002387e656880] Writing block at offset 14039, size 2481, pts 300, dts 300, duration 100, keyframe 0
[out_0_0 @ 000002387e743d60] EOF on sink link out_0_0:default.
No more output streams to write to, finishing.
[webm @ 000002387e656880] end duration = 400
[webm @ 000002387e656880] stream 0 end duration = 400
frame=    4 fps=0.0 q=0.0 Lsize=      17kB time=00:00:00.30 bitrate= 457.8kbits/s speed=4.45x    
video:16kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 4.413191%
Input file #0 (in.webm):
  Input stream #0:0 (video): 4 packets read (34992 bytes); 4 frames decoded; 
  Total: 4 packets (34992 bytes) demuxed
Output file #0 (out.webm):
  Output stream #0:0 (video): 4 frames encoded; 4 packets muxed (16496 bytes); 
  Total: 4 packets (16496 bytes) muxed
4 frames successfully decoded, 0 decoding errors
[AVIOContext @ 000002387e698c20] Statistics: 14 seeks, 10 writeouts
[AVIOContext @ 000002387cc773e0] Statistics: 71649 bytes read, 0 seeks


  


• avcodec_receive_packet() doesn't see the output

  1er mars 2018, par Eugene Alexeev

  I’m trying to create a converter which will make a video out of set of images. Everything is at its place, AVFormatContext, AVCodecContext, AVCodec. I’m creating YUV AVFrame out of UIImage and send it to encoder by avcodec_send_frame() method. Everything goes fine until I’m trying to get AVPacket with method avcodec_receive_packet(). Every time it returns -53 which means - output is not available in the current state - user must try to send input. As I said, I’m sending an input before I’m trying to get something and sending is successful.

  Here’s my code :

  Init ffmpeg entities :

  - (BOOL)setupForConvert:(DummyFVPVideoFile *)videoFile outputPath:(NSString *)path
  
  {
  
      if (!videoFile) {
  
          [self.delegate convertationFailed:@"VideoFile is nil!"];
  
          return NO;
  
      }
  
      currentVideoFile = videoFile;
  
      outputPath = path;
  
      BOOL success = NO;
  
  
  
      success = [self initFormatCtxAndCodecs:path];
  
      if (!success) {
  
          return NO;
  
      }
  
  
  
      success = [self addCameraStreams:videoFile];
  
      if (!success) {
  
          return NO;
  
      }
  
  
  
      success = [self openIOContext:path];
  
      if (!success) {
  
          return NO;
  
      }
  
  
  
      return YES;
  
  }
  
  
  
  - (BOOL)initFormatCtxAndCodecs:(NSString *)path
  
  {
  
      //AVOutputFormat *fmt = av_guess_format("mp4", NULL, NULL);
  
      int ret = avformat_alloc_output_context2(&pFormatCtx, NULL, NULL, [path UTF8String]);
  
      if (ret < 0) {
  
          NSLog(@"Couldn't create output context");
  
          return NO;
  
      }
  
  
  
      //encoder codec init
  
      pCodec = avcodec_find_encoder(AV_CODEC_ID_H264);
  
      if (!pCodec) {
  
          NSLog(@"Couldn't find a encoder codec!");
  
          return NO;
  
      }
  
  
  
      pCodecCtx = avcodec_alloc_context3(pCodec);
  
      if (!pCodecCtx) {
  
          NSLog(@"Couldn't alloc encoder codec context!");
  
          return NO;
  
      }
  
  
  
      pCodecCtx->codec_tag = AV_CODEC_ID_H264;
  
      pCodecCtx->bit_rate = 400000;
  
      pCodecCtx->width = currentVideoFile.size.width;
  
      pCodecCtx->height = currentVideoFile.size.height;
  
      pCodecCtx->time_base = (AVRational){1, (int)currentVideoFile.framerate};
  
      pCodecCtx->framerate = (AVRational){(int)currentVideoFile.framerate, 1};
  
      pCodecCtx->gop_size = 10;
  
      pCodecCtx->max_b_frames = 1;
  
      pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
  
          NSLog(@"Couldn't open the encoder codec!");
  
          return NO;
  
      }
  
  
  
      pPacket = av_packet_alloc();
  
  
  
      return YES;
  
  }
  
  
  
  - (BOOL)addCameraStreams:(DummyFVPVideoFile *)videoFile
  
  {
  
      AVCodecParameters *params = avcodec_parameters_alloc();
  
      if (!params) {
  
          NSLog(@"Couldn't allocate codec parameters!");
  
          return NO;
  
      }
  
  
  
      if (avcodec_parameters_from_context(params, pCodecCtx) < 0) {
  
          NSLog(@"Couldn't copy parameters from context!");
  
          return NO;
  
      }
  
  
  
      for (int i = 0; i < videoFile.idCameras.count - 1; i++)
  
      {
  
          NSString *path = [videoFile.url URLByAppendingPathComponent:videoFile.idCameras[i]].path;
  
          AVStream *stream = avformat_new_stream(pFormatCtx, pCodec);
  
          if (!stream) {
  
              NSLog(@"Couldn't alloc stream!");
  
              return NO;
  
          }
  
  
  
          if (avcodec_parameters_copy(stream->codecpar, params) < 0) {
  
              NSLog(@"Couldn't copy parameters into stream!");
  
              return NO;
  
          }
  
  
  
          stream->avg_frame_rate.num = videoFile.framerate;
  
          stream->avg_frame_rate.den = 1;
  
          stream->codecpar->codec_tag = 0;    //some silly workaround
  
          stream->index = i;
  
          streams[path] = [[VideoStream alloc] initWithStream:stream];
  
      }
  
  
  
      return YES;
  
  }
  
  
  
  - (BOOL)openIOContext:(NSString *)path
  
  {
  
      AVIOContext *ioCtx = nil;
  
      if (avio_open(&ioCtx, [path UTF8String], AVIO_FLAG_WRITE) < 0) {
  
          return NO;
  
      }
  
      pFormatCtx->pb = ioCtx;
  
  
  
      return YES;
  
  }

  And here’s convertation process :

  - (void)launchConvert:(DummyFVPVideoFile *)videoFile
  
  {
  
      BOOL convertInProgress = YES;
  
      unsigned int frameCount = 1;
  
      unsigned long pts = 0;
  
      BOOL success = NO;
  
  
  
      success = [self writeHeader];
  
      if (!success) {
  
          NSLog(@"Couldn't write header!");
  
          return;
  
      }
  
  
  
      AVRational defaultTimeBase;
  
      defaultTimeBase.num = 1;
  
      defaultTimeBase.den = videoFile.framerate;
  
      AVRational streamTimeBase = streams.allValues.firstObject.stream->time_base;
  
  
  
      while (convertInProgress)
  
      {
  
          pts += av_rescale_q(1, defaultTimeBase, streamTimeBase);
  
          for (NSString *path in streams.allKeys)
  
          {
  
              UIImage *img = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%u.jpg", path, frameCount]];
  
              AVPacket *pkt = [self getAVPacket:img withPts:pts];
  
              if (!pkt->data) {   continue;   }
  
              pkt->stream_index = streams[path].stream->index;
  
              //check all settings of pkt
  
  
  
              if (![self writePacket:pkt]) {
  
                  NSLog(@"Couldn't write packet!");
  
                  convertInProgress = NO;
  
                  break;
  
              }
  
          }
  
  
  
          frameCount++;
  
      }
  
  
  
      success = [self writeTrailer];
  
      if (!success) {
  
          NSLog(@"Couldn't write trailer!");
  
          return;
  
      }
  
  
  
      NSLog(@"Convertation finished!");
  
      //delegate convertationFinished method
  
  }
  
  
  
  - (BOOL)writeHeader
  
  {
  
      if (avformat_write_header(pFormatCtx, NULL) < 0) {
  
          return NO;
  
      }
  
  
  
      return YES;
  
  }
  
  
  
  - (BOOL)writePacket:(AVPacket *)pkt
  
  {
  
      if (av_interleaved_write_frame(pFormatCtx, pkt) != 0) {
  
          return NO;
  
      }
  
  
  
      return YES;
  
  }
  
  
  
  - (BOOL)writeTrailer
  
  {
  
      if (av_write_trailer(pFormatCtx) != 0) {
  
          return NO;
  
      }
  
  
  
      return YES;
  
  }
  
  
  
  
  
  /**
  
   This method will create AVPacket out of UIImage.
  
  
  
   @return AVPacket
  
   */
  
  - (AVPacket *)getAVPacket:(UIImage *)img withPts:(unsigned long)pts
  
  {
  
      if (!img) {
  
          NSLog(@"imgData is nil!");
  
          return nil;
  
      }
  
      uint8_t *imgData = [self getPixelDataFromImage:img];
  
  
  
      AVFrame *frame_yuv = av_frame_alloc();
  
      if (!frame_yuv) {
  
          NSLog(@"frame_yuv is nil!");
  
          return nil;
  
      }
  
      frame_yuv->format = AV_PIX_FMT_YUV420P;
  
      frame_yuv->width = (int)img.size.width;
  
      frame_yuv->height = (int)img.size.height;
  
  
  
      int ret = av_image_alloc(frame_yuv->data,
  
                                 frame_yuv->linesize,
  
                                 frame_yuv->width,
  
                                 frame_yuv->height,
  
                                 frame_yuv->format,
  
                                 32);
  
      if (ret < 0) {
  
          NSLog(@"Couldn't alloc yuv frame!");
  
          return nil;
  
      }
  
  
  
      struct SwsContext *sws_ctx = nil;
  
      sws_ctx = sws_getContext((int)img.size.width, (int)img.size.height, AV_PIX_FMT_RGB24,
  
                               (int)img.size.width, (int)img.size.height, AV_PIX_FMT_YUV420P,
  
                               0, NULL, NULL, NULL);
  
      const uint8_t *scaleData[1] = { imgData };
  
      int inLineSize[1] = { 4 * img.size.width };
  
      sws_scale(sws_ctx, scaleData, inLineSize, 0, (int)img.size.height, frame_yuv->data, frame_yuv->linesize);
  
  
  
      frame_yuv->pict_type = AV_PICTURE_TYPE_I;
  
      frame_yuv->pts = pCodecCtx->frame_number;
  
  
  
      ret = avcodec_send_frame(pCodecCtx, frame_yuv);   //every time everything is fine
  
      if (ret != 0) {
  
          NSLog(@"Couldn't send yuv frame!");
  
          return nil;
  
      }
  
  
  
      av_init_packet(pPacket);
  
      pPacket->dts = pPacket->pts = pts;
  
      do {
  
          ret = avcodec_receive_packet(pCodecCtx, pPacket);   //every time -35 error
  
          NSLog(@"ret = %d", ret);
  
          if (ret == AVERROR_EOF) {
  
              NSLog(@"AVERROR_EOF!");
  
          } else if (ret == AVERROR(EAGAIN)) {
  
              NSLog(@"AVERROR(EAGAIN)");
  
          } else if (ret == AVERROR(EINVAL)) {
  
              NSLog(@"AVERROR(EINVAL)");
  
          }
  
          if (ret != 0) {
  
              NSLog(@"Couldn't receive packet!");
  
              //return nil;
  
          }
  
      } while ( ret == 0 );
  
  
  
      free(imgData);
  
      av_packet_unref(pPacket);
  
      av_packet_free(pPacket);
  
      av_frame_unref(&frame_yuv);
  
      av_frame_free(&frame_yuv);
  
      //perform other clean up and test dat shit
  
  
  
      return pPacket;
  
  }

  Any insights would be helpful. Thanks !

• swscaler bad src image pointers

  7 mars 2018, par user1496491

  I’m completely lost. I’m trying to capture 30 screenshots and put them into a video with FFMPEG under Windows 10. And it keeps telling me that [swscaler @ 073890a0] bad src image pointers. As a result the video is entirely green. If I change format to dshow using video=screen-capture-recorder the video looks to be mostly garbage. Here’s my short code for that. I’m completely stuck and don’t know even in which direction to look.

  MainWindow.h

  #ifndef MAINWINDOW_H
  
  #define MAINWINDOW_H
  
  
  
  #include <qmainwindow>
  
  #include <qfuture>
  
  #include <qfuturewatcher>
  
  #include <qmutex>
  
  #include <qmutexlocker>
  
  
  
  extern "C" {
  
  #include "libavcodec/avcodec.h"
  
  #include "libavcodec/avfft.h"
  
  
  
  #include "libavdevice/avdevice.h"
  
  
  
  #include "libavfilter/avfilter.h"
  
  #include "libavfilter/avfiltergraph.h"
  
  #include "libavfilter/buffersink.h"
  
  #include "libavfilter/buffersrc.h"
  
  
  
  #include "libavformat/avformat.h"
  
  #include "libavformat/avio.h"
  
  
  
  #include "libavutil/opt.h"
  
  #include "libavutil/common.h"
  
  #include "libavutil/channel_layout.h"
  
  #include "libavutil/imgutils.h"
  
  #include "libavutil/mathematics.h"
  
  #include "libavutil/samplefmt.h"
  
  #include "libavutil/time.h"
  
  #include "libavutil/opt.h"
  
  #include "libavutil/pixdesc.h"
  
  #include "libavutil/file.h"
  
  
  
  #include "libswscale/swscale.h"
  
  }
  
  
  
  class MainWindow : public QMainWindow
  
  {
  
      Q_OBJECT
  
  
  
  public:
  
      MainWindow(QWidget *parent = 0);
  
      ~MainWindow();
  
  
  
  private:
  
      AVFormatContext *inputFormatContext = nullptr;
  
      AVFormatContext *outFormatContext = nullptr;
  
  
  
      AVStream* videoStream = nullptr;
  
  
  
      AVDictionary* options = nullptr;
  
  
  
      AVCodec* outCodec = nullptr;
  
      AVCodec* inputCodec = nullptr;
  
      AVCodecContext* inputCodecContext = nullptr;
  
      AVCodecContext* outCodecContext = nullptr;
  
      SwsContext* swsContext = nullptr;
  
  
  
  private:
  
      void init();
  
      void initOutFile();
  
      void collectFrame();
  
  };
  
  
  
  #endif // MAINWINDOW_H
  
  </qmutexlocker></qmutex></qfuturewatcher></qfuture></qmainwindow>

  MainWindow.cpp

  #include "MainWindow.h"
  
  
  
  #include <qguiapplication>
  
  #include <qlabel>
  
  #include <qscreen>
  
  #include <qtimer>
  
  #include <qlayout>
  
  #include <qimage>
  
  #include <qtconcurrent></qtconcurrent>QtConcurrent>
  
  #include <qthreadpool>
  
  
  
  #include "ScreenCapture.h"
  
  
  
  MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
  
  {
  
      resize(800, 600);
  
  
  
      auto label = new QLabel();
  
      label->setAlignment(Qt::AlignHCenter | Qt::AlignVCenter);
  
  
  
      auto layout = new QHBoxLayout();
  
      layout->addWidget(label);
  
  
  
      auto widget = new QWidget();
  
      widget->setLayout(layout);
  
      setCentralWidget(widget);
  
  
  
      init();
  
      initOutFile();
  
      collectFrame();
  
  }
  
  
  
  MainWindow::~MainWindow()
  
  {
  
      avformat_close_input(&amp;inputFormatContext);
  
      avformat_free_context(inputFormatContext);
  
  
  
      QThreadPool::globalInstance()->waitForDone();
  
  }
  
  
  
  void MainWindow::init()
  
  {
  
      av_register_all();
  
      avcodec_register_all();
  
      avdevice_register_all();
  
      avformat_network_init();
  
  
  
      auto screen = QGuiApplication::screens()[0];
  
      QRect geometry = screen->geometry();
  
  
  
      inputFormatContext = avformat_alloc_context();
  
  
  
      options = NULL;
  
      av_dict_set(&amp;options, "framerate", "30", NULL);
  
      av_dict_set(&amp;options, "offset_x", QString::number(geometry.x()).toLatin1().data(), NULL);
  
      av_dict_set(&amp;options, "offset_y", QString::number(geometry.y()).toLatin1().data(), NULL);
  
      av_dict_set(&amp;options, "video_size", QString(QString::number(geometry.width()) + "x" + QString::number(geometry.height())).toLatin1().data(), NULL);
  
      av_dict_set(&amp;options, "show_region", "1", NULL);
  
  
  
      AVInputFormat* inputFormat = av_find_input_format("gdigrab");
  
      avformat_open_input(&amp;inputFormatContext, "desktop", inputFormat, &amp;options);
  
  
  
      int videoStreamIndex = av_find_best_stream(inputFormatContext, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
  
  
  
      inputCodecContext = inputFormatContext->streams[videoStreamIndex]->codec;
  
      inputCodecContext->width = geometry.width();
  
      inputCodecContext->height = geometry.height();
  
      inputCodecContext->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      inputCodec = avcodec_find_decoder(inputCodecContext->codec_id);
  
      avcodec_open2(inputCodecContext, inputCodec, NULL);
  
  }
  
  
  
  void MainWindow::initOutFile()
  
  {
  
      const char* filename = "C:/Temp/output.mp4";
  
  
  
      avformat_alloc_output_context2(&amp;outFormatContext, NULL, NULL, filename);
  
  
  
      outCodec = avcodec_find_encoder(AV_CODEC_ID_MPEG4);
  
  
  
      videoStream = avformat_new_stream(outFormatContext, outCodec);
  
      videoStream->time_base = {1, 30};
  
  
  
      outCodecContext = videoStream->codec;
  
      outCodecContext->codec_id = AV_CODEC_ID_MPEG4;
  
      outCodecContext->codec_type = AVMEDIA_TYPE_VIDEO;
  
      outCodecContext->pix_fmt = AV_PIX_FMT_YUV420P;
  
      outCodecContext->bit_rate = 400000;
  
      outCodecContext->width = inputCodecContext->width;
  
      outCodecContext->height = inputCodecContext->height;
  
      outCodecContext->gop_size = 3;
  
      outCodecContext->max_b_frames = 2;
  
      outCodecContext->time_base = videoStream->time_base;
  
  
  
      if (outFormatContext->oformat->flags &amp; AVFMT_GLOBALHEADER)
  
          outCodecContext->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  
  
  
      avcodec_open2(outCodecContext, outCodec, NULL);
  
  
  
      if (!(outFormatContext->flags &amp; AVFMT_NOFILE))
  
          avio_open2(&amp;outFormatContext->pb, filename, AVIO_FLAG_WRITE, NULL, NULL);
  
  
  
      swsContext = sws_getContext(inputCodecContext->width,
  
                                  inputCodecContext->height,
  
                                  inputCodecContext->pix_fmt,
  
                                  outCodecContext->width,
  
                                  outCodecContext->height,
  
                                  outCodecContext->pix_fmt,
  
                                  SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
      avformat_write_header(outFormatContext, &amp;options);
  
  }
  
  
  
  void MainWindow::collectFrame()
  
  {
  
      AVFrame* frame = av_frame_alloc();
  
      frame->data[0] = NULL;
  
      frame->width = inputCodecContext->width;
  
      frame->height = inputCodecContext->height;
  
      frame->format = inputCodecContext->pix_fmt;
  
  
  
      av_image_alloc(frame->data, frame->linesize, inputCodecContext->width, inputCodecContext->height, (AVPixelFormat)frame->format, 32);
  
  
  
      AVFrame* outFrame = av_frame_alloc();
  
      outFrame->data[0] = NULL;
  
      outFrame->width = outCodecContext->width;
  
      outFrame->height = outCodecContext->height;
  
      outFrame->format = outCodecContext->pix_fmt;
  
  
  
      av_image_alloc(outFrame->data, outFrame->linesize, outCodecContext->width, outCodecContext->height, (AVPixelFormat)outFrame->format, 32);
  
  
  
      int bufferSize = av_image_get_buffer_size(outCodecContext->pix_fmt,
  
                                                outCodecContext->width,
  
                                                outCodecContext->height,
  
                                                24);
  
  
  
      uint8_t* outBuffer = (uint8_t*)av_malloc(bufferSize);
  
  
  
      avpicture_fill((AVPicture*)outFrame, outBuffer,
  
                     AV_PIX_FMT_YUV420P,
  
                     outCodecContext->width, outCodecContext->height);
  
  
  
      int frameCount = 30;
  
      int count = 0;
  
  
  
      AVPacket* packet = (AVPacket*)av_malloc(sizeof(AVPacket));
  
      av_init_packet(packet);
  
  
  
      while(av_read_frame(inputFormatContext, packet) >= 0)
  
      {
  
          if(packet->stream_index == videoStream->index)
  
          {
  
              int frameFinished = 0;
  
              avcodec_decode_video2(inputCodecContext, frame, &amp;frameFinished, packet);
  
  
  
              if(frameFinished)
  
              {
  
                  if(++count > frameCount)
  
                  {
  
                      qDebug() &lt;&lt; "FINISHED!";
  
                      break;
  
                  }
  
  
  
                  sws_scale(swsContext, frame->data, frame->linesize, 0, inputCodecContext->height, outFrame->data, outFrame->linesize);
  
  
  
                  AVPacket outPacket;
  
                  av_init_packet(&amp;outPacket);
  
                  outPacket.data = NULL;
  
                  outPacket.size = 0;
  
  
  
                  int got_picture = 0;
  
                  avcodec_encode_video2(outCodecContext, &amp;outPacket, outFrame, &amp;got_picture);
  
  
  
                  if(got_picture)
  
                  {
  
                      if(outPacket.pts != AV_NOPTS_VALUE) outPacket.pts = av_rescale_q(outPacket.pts, videoStream->codec->time_base, videoStream->time_base);
  
                      if(outPacket.dts != AV_NOPTS_VALUE) outPacket.dts = av_rescale_q(outPacket.dts, videoStream->codec->time_base, videoStream->time_base);
  
  
  
                      av_write_frame(outFormatContext , &amp;outPacket);
  
                  }
  
  
  
                  av_packet_unref(&amp;outPacket);
  
              }
  
          }
  
      }
  
  
  
      av_write_trailer(outFormatContext);
  
  
  
      av_free(outBuffer);
  
  }
  
  </qthreadpool></qimage></qlayout></qtimer></qscreen></qlabel></qguiapplication>