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• How can I create a side-by-side horizontally stacked video with a delay in video and audio using ffmpeg-python ?

  3 septembre 2021, par kup

  I am trying to create a video from two videos that will be stacked horizontally, but the resulting video is not what I expected. The same video is appearing on both sides (left and right). How can that be achieved ?

  


  The ffmpeg command I tried, which kind of worked :

  


  ffmpeg -i left.mp4 -i right.mp4 -filter_complex "
[0:v]setpts=PTS-STARTPTS[l];
[1:v]setpts=PTS-STARTPTS,tpad=start_duration=14:start_mode=add:color=black[r];
[l][r]hstack=inputs=2[stacked]; [0:a][1:a]amix=inputs=2[a]
" -map "[stacked]" -map "[a]" -c:a aac -preset superfast result.mp4


  


  The ffmpeg-python script that's not working :

  


  in0 = ffmpeg.input('0.mp4')
in1 = ffmpeg.input('right.mkv')
aout = ffmpeg.filter([in0.audio, in1.audio.filter('adelay', "5000|5000")],'amix')
vout = ffmpeg.filter([inv0.video, inv1.video.filter('tpad', start_duration=5, start_mode='add', color='black')], 'hstack')

(
    ffmpeg
    .concat(vout, aout, v=1, a=1)
    .output("out.mkv")
    .run()
)


  


  This script is not resulting in the expected output which is two videos side-by-side horizontally stacked.

  


• Trying to save frames as colored image using Ffmpeg in C++

  2 septembre 2021, par Tolga

  I am new to FFmpeg and I am trying to save the video frames as colored images. I have achieved saving them as grayscale using Netpbm, however, I need to save the frames as colored. I have tried implementing the code in this link.

  


  However, I get an error :

  


  'Exception thrown at 0x00E1FC4F (swscale-5.dll) in VideoDecoding2.exe:
 0xC0000005: Access violation writing location 0xCCCCCCCC.'


  


  Is there any way to improve this code or another way to save frames as colored ?

  


  Here is my code below.

  


  

  • src_pix_fmt is AV_PIX_FMT_YUV420p.

  


  • dst_pix_fmt is AV_PIX_FMT_RGB24.

  


  


  src_pix_fmt = avcc->pix_fmt;

src_width = avcc->width;
src_height = avcc->height;

dst_width = src_width;
dst_height = src_height;

numBytes = av_image_get_buffer_size(dst_pix_fmt, dst_width, dst_height, 0);

buffer = (uint8_t*)av_malloc(numBytes);

if ((ret = av_image_alloc(src_data, src_linesize, src_width, src_height, src_pix_fmt, 16)) < 0)
{
    printf("Couldn't allocate source image.\n");
    return 0;
}

av_image_fill_arrays(frameRGB->data, frameRGB->linesize, buffer, dst_pix_fmt, dst_width, dst_height, 0);

while (av_read_frame(avfc, packet) >= 0)
{
    ret = avcodec_send_packet(avcc, packet);
    if (ret < 0)
    {
        printf("Packets could not supplied to decoder.\n");
        return -1;
    }

    ret = avcodec_receive_frame(avcc, frame);
    printf("%d", ret);

    if (packet->stream_index == videoStream)
    {
        sws_ctx = sws_getContext(src_width, src_height, src_pix_fmt,
            dst_width, dst_height, dst_pix_fmt,
            SWS_BILINEAR, NULL, NULL, NULL);

        if (!sws_ctx)
        {
            printf("Cannot create scale context for conversion\n"
                "fmt:%s s:%dx%d --> fmt:%s s:%dx%d\n",
                av_get_pix_fmt_name(src_pix_fmt), src_width, src_height,
                av_get_pix_fmt_name(dst_pix_fmt), dst_width, dst_height);
            return 0;
        }

        sws_scale(sws_ctx, (const uint8_t* const*)frame->data, frame->linesize, 0, frame->height, dst_data, dst_linesize);

        FILE* f;
        char szFilename[32];
        int y;

        snprintf(szFilename, sizeof(szFilename), "frame%d.ppm", avcc->frame_number);
        fopen_s(&f, szFilename, "wb");
        
        if (f == NULL)
        {
            printf("Couldn't open file.\n");
            return 0;
        }
        
        fprintf(f, "P6\n%d %d\n255\n", dst_width, dst_height);

        for (y = 0; y < dst_height; y++)
            fwrite(frameRGB->data[0] + y * frameRGB->linesize[0], 1, dst_width * 3, f);
        
        fclose(f);
    }
}


  


• LibVLC : Is a filter like v360:fisheye from ffmpeg available in LibVLC ?

  8 septembre 2021, par Craab

  I'm having problem playing fisheye(180) videos panoramically on the fly
using LibVlcSharp in a WinForms appliction.

  


  More specifically : what I want to do is filtering video with libvlcsharp in a WinForms application(c#) with the same effect like

  


  -vf v360=fisheye:e:ih_fov=180:iv_fov=180:pitch=90


  


  from ffmpeg.

  


  FYI : this will not make the video tagged with equirectanglar projection, the v360=fisheye filter dewarps the video and the video stays rectanglar.

  


  The input video is like this :

  


  

  


  And the the expected output should be like :

  


  

  


  This can be achieved by :

  


  ./ffmpeg -i input.mov  -vf v360=fisheye:e:ih_fov=180:iv_fov=180:pitch=90,crop=in_w:in_h/2:in_w:in_h/2 output.mov


  


  but I need to do this with LibVLC and on the fly.

  


  Can I achieve this with LibVLC's video filter ?

  


  Or I need to develop my own filter and make a wrapper for c# ?