Newest 'ffmpeg' Questions - Stack Overflow

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  • Convert WebM/H.264 to MP4/H.264 efficiently with ffmpeg.js

    31 juillet 2017, par SB2055

    As a result of the answer here: Recording cross-platform (H.264?) videos using WebRTC MediaRecorder

    How can one go about using ffmpeg.js to efficiently unwrap a webm h.264 video and re-wrap it into an mp4 container?

    I'm looking through the docs: https://github.com/Kagami/ffmpeg.js?files=1

    However I don't see (or perhaps I'm looking for the wrong terminology) any examples for the above. This operation will be performed on the browser (chrome) prior to uploading as a Blob - I could use a web worker though hopefully rewrapping is a trivial enough operation to not require it.

  • FFmpeg - CRF Command for Nvenc encode ? [migrated]

    31 juillet 2017, par hongducwb

    My current command for resize videos, 1080p 2GB to 300MB but it take a lot of time on my CPU

    mkdir newfiles
    for %%a in ("*.mp4") do ffmpeg -i "%%a" -c:v libx264 -preset slow -crf 21 c:a aac -b:a 128k -vf scale=678:-2 "newfiles\%%~na.mp4"
    pause

    i try nvenc with my 1070.

    mkdir newfiles
    for %%a in ("*.mp4") do ffmpeg -i "%%a" -c:v h264_nvenc -preset slow -c:a aac -b:a 128k -vf scale=678:-2 "newfiles\%%~na.mp4"
    pause

    output size always 3x or 5x original size, nvenc not working with -crf

    so anyone know command to resize/convert video with high quality and small size ?
    and should i use gpu for encoding ?

    THANK

  • ffmpeg showing "Error initializing output stream 0:0"

    31 juillet 2017, par user2565010

    I am running the following command

    ffmpeg -i DJI_0001.MOV DJI_0001.mp4

    in order to convert the video to mp4 from MOV with no other property changes.

    The issue is that I am getting:

    ffmpeg version N-86863-g2ba20d799a-static http://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.4.0 (Debian 6.4.0-2) 20170724
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-6 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gray --enable-libass --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libzimg
  libavutil      55. 69.100 / 55. 69.100
  libavcodec     57.102.100 / 57.102.100
  libavformat    57. 76.100 / 57. 76.100
  libavdevice    57.  7.100 / 57.  7.100
  libavfilter     6. 95.100 /  6. 95.100
  libswscale      4.  7.101 /  4.  7.101
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'DJI_0001.MOV':
  Metadata:
    major_brand     : qt  
    minor_version   : 538182144
    compatible_brands: qt  
    creation_time   : 2017-07-23T17:04:58.000000Z
    location        : 
    location-{    : 
    comment         : 0.9.142
  Duration: 00:00:17.89, start: 0.000000, bitrate: 60017 kb/s
    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 4096x2160 [SAR 1:1 DAR 256:135], 60014 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
    Metadata:
      creation_time   : 2017-07-23T17:04:58.000000Z
      handler_name    : DJI.AVC
      encoder         : Dji AVC encoder
File 'DJI_0001.mp4' already exists. Overwrite ? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x3ed56a0] using SAR=1/1
[libx264 @ 0x3ed56a0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
Conversion failed!

    I see no other error message that would indicate an underlying problem. Could anybody please give me some info on how should I fix it?

  • FFMPEG skipping chunks from the video

    31 juillet 2017, par Swapnil Konde

    We are transcoding videos by using the following command:

    ffmpeg -y -i cccb3694bbc74dcdbecf3d99851f529e_17504 -loglevel error -c:v libx264 -pix_fmt yuv420p -movflags +faststart -preset medium -b:v 1560k -crf 24 -pass 1 -passlogfile cccb3694bbc74dcdbecf3d99851f529e_17504.log -c:a aac -b:a 256k -s 400x720 -f mp4 /dev/null 2>&1 && ffmpeg -y -i cccb3694bbc74dcdbecf3d99851f529e_17504 -loglevel error -c:v libx264 -pix_fmt yuv420p -movflags +faststart -preset medium -b:v 1560k -crf 24 -pass 2 -passlogfile cccb3694bbc74dcdbecf3d99851f529e_17504.log -c:a aac -b:a 256k -s 400x720 cccb3694bbc74dcdbecf3d99851f529e_17504.mp4 2>&1

    And while streaming we are creating chunks which consist below steps:

    1. decoding the frames and
    2. changing the bandwidth as per our convenience and
    3. encoding the packet again.

    But we are observing frame skipping in chunks, which makes video shorter by 1 or 2 seconds. We have used ffmpeg 3.0 and transcoding examples given on the ffmpeg site.

  • c# ffmpeg encode/decode audio and video

    31 juillet 2017, par IC.Fulvio

    I'm writing C# code to stream audio and video through RTSP. I use ffmpe.Autogen wrapper and NAudio. With the video I have no problem, hevc 25fps.

    About audio, I capture audio samples with NAudio and after, I copy the buffer in the AVframe data of ffmpeg. The audio codec that I use is: AAC f32le 44,1 khz. When I encode, in the main loop, I write one video frame and after one audio frame. 

    while (video_st != null)
        {

            img1.CopyTo(imgframe);
            var startFrame = DateTime.Now;

            ret = Utility_ffmpeg.write_video_frame(outContext, video_st, frameCount, &dst_picture, frame, ref imgframe, sws_ctx);

            if (ret < 0)
            {
                Debug.WriteLine("Write video frame failed.\n");
                return;
            }

            var streamDuration = DateTime.Now - startSend;

            //audio
            if (enable_audio && srcAudio.audio_buff != null)
                {

                if (srcAudio.audio_buff_dim > 0)
                {
                    lock (srcAudio.audio_buff)
                    {
                        frameCount++;
                        Utility_ffmpeg.write_audio_frame(outContext, srcAudio.audio_buff, srcAudio.audio_buff_dim, audio_st, frameCount);
                    }
                }
            }

            Debug.WriteLine("Elapsed time " + streamDuration + ", video stream pts " + video_st->pts.val + ".\n");

            var frameDuration = DateTime.Now - startFrame;
            Debug.WriteLine(frameDuration+" total \n");
            //System.Threading.Thread.Sleep((int)((long)1000.0 / (long)STREAM_FRAME_RATE - (long)frameDuration.TotalSeconds));
            System.Threading.Thread.Sleep(40);

            //}
        }

    When I decode the video all is ok but the audio comes and goes. The synchronization is ok. I think the problem is that I need to send more audio frame then video, but I'm not sure. Someone has an idea about the origin of the problem? Thanks in advance and sorry for my English.

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