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• How to record an HTML animation and save it as a video, in an automated manner in the backend

  14 mai 2022, par frizurd

  I need to record a webpage and save it as a video, in an automated manner, without human interaction.

  


  I am creating a NodeJS app that generates MP4 videos on the request of the user. The user provides an MP3 file, the app generates animated waveforms for the sound file on top of an illustration.

  


  What I came up with so far is a system that opens a generated web page in the backend, plays the audio file, and shows audio visualization for the audio file on an HTML canvas element. On top of another canvas with mainly static components, such as images, that do not animate. The system records this, the output will be a video file. Finally, I will merge the video file with the sound file to create the final file for the user.

  


  I came up with 2 possible solutions but both of them have problems which I am not able to solve at the moment.

  


  ---

  


  Solution #1

  


  Use a headless browser API such as Phantomjs or Puppeteer to snatch a screenshot x time every second and pipe it to FFmpeg.

  


  The problem

  


  The problem with this is that the process is not realtime. It would work fine if it's JUST an animation but mine is dependant on the audio file. The audio file will play-on during the render which results in a glitchy 1FPS-esque video.

  


  Possible solution ?

  


  Don't play the audio file live but convert the audio file into raw data. Animate the audio visualization based on the raw data instead.
Not sure how to do this and if it's even possible.

  


  ---

  


  Solution #2

  


  Play, record, and save the animation, all in the frontend.
Could use ccapture.js to record and save a canvas.
Use a headless browser to open the page and save it to disk when it's done playing.
Doesn't sound like it's the best solution.

  


  The problem(s)

  


  I have more than 1 canvas.
It takes a while, especially when the audio file is longer than 10 minutes.
Making users wait for a long time can be a deal-breaker.

  


  Possible solution ?

  


  Merge canvases into one.

  


  No idea how to speed up the rendering time and I doubt it's possible this way.

  


• 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);
    }
}


  


• How to install ffmpeg on Google App Engine ?

  3 mai 2020, par UtkuBulkan

  I intend to install ffmpeg and ffprobe to my Google App Engine flex environment, how can I do this with requirements.txt as a package ?

  



  I am currently using ffmpeg-python yet, this is only a wrapper.

  



  ffmpeg-python==0.2.0
ffprobe-python==1.0.3


  



  Below is the error when I try to use ffmpeg-python wrapper, which is expected as there is no ffmpeg and ffprobe available :

  



  2020-05-03 11:42:36 default[20200503t112932]  [03/May/2020 11:42:36] ERROR    [log.py:228] Internal Server Error: /capture_thumbnail/
2020-05-03 11:42:36 default[20200503t112932]  Traceback (most recent call last):    File "/env/lib/python3.6/site-packages/django/core/handlers/exception.py", line 34, in inner      response = get_response(request)    File "/env/lib/python3.6/site-packages/django/core/handlers/base.py", line 115, in _get_response      response = self.process_exception_by_middleware(e, request)    File "/env/lib/python3.6/site-packages/django/core/handlers/base.py", line 113, in _get_response      response = wrapped_callback(request, *callback_args, **callback_kwargs)    File "/home/vmagent/app/core/views.py", line 62, in capture_thumbnail      generate_thumbnail(request, blob_uuid)    File "/home/vmagent/app/core/videointelligence1.py", line 264, in generate_thumbnail      probe = ffmpeg.probe(video_url)    File "/env/lib/python3.6/site-packages/ffmpeg/_probe.py", line 20, in probe      p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)    File "/opt/python3.6/lib/python3.6/subprocess.py", line 729, in __init__      restore_signals, start_new_session)    File "/opt/python3.6/lib/python3.6/subprocess.py", line 1364, in _execute_child      raise child_exception_type(errno_num, err_msg, err_filename)  FileNotFoundError: [Errno 2] No such file or directory: 'ffprobe': 'ffprobe'


  



  Can you please suggest a way, so I can use ffprobe on Google App Engine.