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• Decode multiple video on GPU (FFmpeg.autogen + C#)

  5 décembre 2024, par Sang Nguyen

  I'm trying to use the basic example about decoding video (FFmpeg.AutoGen.Example) in the FFmpeg.autogen 4.3.0.3 library https://github.com/Ruslan-B/FFmpeg.AutoGen to decode multiple videos on a GPU (AMD radeon R7 430). My main function is as follows :

  


   private static void Main(string[] args)
        {
            var url = @".\abc.mp4";
            for (int i = 0; i < 11; i++)
            {
                url = @"D:\video\abc" + i + ".mp4";
                new Thread(() =>
                {
                    DecodeAllFramesToImages(AVHWDeviceType.AV_HWDEVICE_TYPE_D3D11VA, url);
                }).Start();
            }
        }


  


  I try to decode video abc.mp4 with GPU Hardware Acceleration. However, an error occurs when i run thread count greater than 10. The error images is as follows :

  


  

  • "System.AccessViolationException : Attempted to read or write protected memory. This is often an indication that other memory." enter image description here

  


  • And in the console screen there is an error message "Failed to create D3D11VA video decoder" and "Failed setup for format d3d11 : hwaccel innitialisation returned error"
enter image description here.

  


  


  I'm new to the ffmpeg library recently, so I don't know the problem very well, I would love to have your help with this error !!

  


  private static unsafe void DecodeAllFramesToImages(AVHWDeviceType HWDevice, string url)
        {             
            using (var vsd = new VideoStreamDecoder(url,HWDevice))
            {
                Console.WriteLine($"codec name: {vsd.CodecName}");

                var info = vsd.GetContextInfo();
                info.ToList().ForEach(x => Console.WriteLine($"{x.Key} = {x.Value}"));

                var sourceSize = vsd.FrameSize;
                var sourcePixelFormat = HWDevice == AVHWDeviceType.AV_HWDEVICE_TYPE_NONE ? vsd.PixelFormat : GetHWPixelFormat(HWDevice);
                var destinationSize = sourceSize;
                var destinationPixelFormat = AVPixelFormat.AV_PIX_FMT_YUV420P;
                using (var vfc = new VideoFrameConverter(sourceSize, sourcePixelFormat, destinationSize, destinationPixelFormat))
                {
                    var frameNumber = 0;
                    while (vsd.TryDecodeNextFrame(out var frame))
                    {
                       //var convertedFrame = vfc.Convert(frame);                        
                       // using (var bitmap = new Bitmap(convertedFrame.width, convertedFrame.height, convertedFrame.linesize[0], PixelFormat.Format24bppRgb, (IntPtr) convertedFrame.data[0]))
                       // bitmap.Save($"frame.{frameNumber:D8}.jpg", ImageFormat.Jpeg);
                        
                        Console.WriteLine($"frame: {frameNumber}");
                        frameNumber++;
                    }
                }
            }
        }


  


  using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Runtime.InteropServices;

namespace FFmpeg.AutoGen.Example
{
    public sealed unsafe class VideoStreamDecoder : IDisposable
    {
        private readonly AVCodecContext* _pCodecContext;
        private readonly AVFormatContext* _pFormatContext;
        private readonly int _streamIndex;
        private readonly AVFrame* _pFrame;
        private readonly AVFrame* _receivedFrame;
        private readonly AVPacket* _pPacket;

        public VideoStreamDecoder(string url, AVHWDeviceType HWDeviceType = AVHWDeviceType.AV_HWDEVICE_TYPE_NONE)
        {
            _pFormatContext = ffmpeg.avformat_alloc_context();
            _receivedFrame = ffmpeg.av_frame_alloc();
            var pFormatContext = _pFormatContext;
            ffmpeg.avformat_open_input(&pFormatContext, url, null, null).ThrowExceptionIfError();
            ffmpeg.avformat_find_stream_info(_pFormatContext, null).ThrowExceptionIfError();
            AVCodec* codec = null;
            _streamIndex = ffmpeg.av_find_best_stream(_pFormatContext, AVMediaType.AVMEDIA_TYPE_VIDEO, -1, -1, &codec, 0).ThrowExceptionIfError();
            _pCodecContext = ffmpeg.avcodec_alloc_context3(codec);
            if (HWDeviceType != AVHWDeviceType.AV_HWDEVICE_TYPE_NONE)
            {
                ffmpeg.av_hwdevice_ctx_create(&_pCodecContext->hw_device_ctx, HWDeviceType, null, null, 0).ThrowExceptionIfError();
            }
            ffmpeg.avcodec_parameters_to_context(_pCodecContext, _pFormatContext->streams[_streamIndex]->codecpar).ThrowExceptionIfError();
            ffmpeg.avcodec_open2(_pCodecContext, codec, null).ThrowExceptionIfError();            
            CodecName = ffmpeg.avcodec_get_name(codec->id);
            FrameSize = new Size(_pCodecContext->width, _pCodecContext->height);
            PixelFormat = _pCodecContext->pix_fmt;
            _pPacket = ffmpeg.av_packet_alloc();
            _pFrame = ffmpeg.av_frame_alloc();
        }

        public string CodecName { get; }
        public Size FrameSize { get; }
        public AVPixelFormat PixelFormat { get; }

        public void Dispose()
        {
            ffmpeg.av_frame_unref(_pFrame);
            ffmpeg.av_free(_pFrame);

            ffmpeg.av_packet_unref(_pPacket);
            ffmpeg.av_free(_pPacket);

            ffmpeg.avcodec_close(_pCodecContext);
            var pFormatContext = _pFormatContext;
            ffmpeg.avformat_close_input(&pFormatContext);
        }

        public bool TryDecodeNextFrame(out AVFrame frame)
        {
            ffmpeg.av_frame_unref(_pFrame);
            ffmpeg.av_frame_unref(_receivedFrame);
            int error;
            do
            {
                try
                {
                    do
                    {
                        error = ffmpeg.av_read_frame(_pFormatContext, _pPacket);
                        if (error == ffmpeg.AVERROR_EOF)
                        {
                            frame = *_pFrame;
                            return false;
                        }

                        error.ThrowExceptionIfError();
                    } while (_pPacket->stream_index != _streamIndex);

                    ffmpeg.avcodec_send_packet(_pCodecContext, _pPacket).ThrowExceptionIfError();
                }
                finally
                {
                    ffmpeg.av_packet_unref(_pPacket);
                }

                error = ffmpeg.avcodec_receive_frame(_pCodecContext, _pFrame);
            } while (error == ffmpeg.AVERROR(ffmpeg.EAGAIN));
            error.ThrowExceptionIfError();
            if (_pCodecContext->hw_device_ctx != null)
            {
                ffmpeg.av_hwframe_transfer_data(_receivedFrame, _pFrame, 0).ThrowExceptionIfError();
                frame = *_receivedFrame;
            }
            else
            {
                frame = *_pFrame;
            }
            return true;
        }
        public IReadOnlyDictionary GetContextInfo()
        {
            AVDictionaryEntry* tag = null;
            var result = new Dictionary();
            while ((tag = ffmpeg.av_dict_get(_pFormatContext->metadata, "", tag, ffmpeg.AV_DICT_IGNORE_SUFFIX)) != null)
            {
                var key = Marshal.PtrToStringAnsi((IntPtr) tag->key);
                var value = Marshal.PtrToStringAnsi((IntPtr) tag->value);
                result.Add(key, value);
            }
            return result;
        }
    }
}


  


• FFmpeg Autogen and Unity C# to generate video from screenshots (FFmpeg.Autogen)

  1er juin 2022, par cameron gibbs

  I've taken the FFmpegHelper, VideoFrameConverter, H264VideoStreamEncoder classes straight from the FFmpeg.AutoGen.Example, rolled my own FFmpegBinariesHelper class and Size struct and mangled the EncodeImagesToH264 from Program.cs to look like the below code. I capture a bunch of frames into textures and feed them into Encoder.EncodeImagesToH264. It produces a file I'm calling outputFileName.h264 just fine, no errors. I've changed H264VideoStreamEncoder a little based on ffmpeg's own c++ examples because they had a few things it seemed the C# example was missing but that hasn't made any difference.

  


  The video is weird :

  


  

  1. it only plays in VLC, is there another AVPixelFormat I should be using for the destinationPixelFormat so that anything can play ?

  


  2. VLC is unable to detect the video length or show current time

  


  3. it plays back weird as if the first few seconds are all the same frame then starts playing what appears to be some of the frames I'd expect

  


  


      public static class Encoder
    {
        public static unsafe void EncodeImagesToH264(Texture2D[] images, int fps, string outputFileName)
        {
            FFmpegBinariesHelper.RegisterFFmpegBinaries();

            var fistFrameImage = images[0];
            outputFileName = Path.ChangeExtension(outputFileName, ".h264");
            var sourceSize = new Size(fistFrameImage.width, fistFrameImage.height);
            var sourcePixelFormat = AVPixelFormat.AV_PIX_FMT_RGB24;
            var destinationSize = sourceSize;
            var destinationPixelFormat = AVPixelFormat.AV_PIX_FMT_YUV420P;

            try
            {
                using (var vfc = new VideoFrameConverter(
                    sourceSize,
                    sourcePixelFormat,
                    destinationSize,
                    destinationPixelFormat))
                {
                    using var fs = File.Open(outputFileName, FileMode.Create);
                    using var vse = new H264VideoStreamEncoder(fs, fps, destinationSize);
                    var frameNumber = 0;
                    foreach (var frameFile in images)
                    {
                        var bitmapData = GetBitmapData(frameFile);

                        //var pBitmapData = (byte*)NativeArrayUnsafeUtility
                        //    .GetUnsafeBufferPointerWithoutChecks(bitmapData);

                        fixed (byte* pBitmapData = bitmapData)
                        {
                            var data = new byte_ptrArray8 { [0] = pBitmapData };
                            var linesize = new int_array8 { [0] = bitmapData.Length / sourceSize.Height };
                            var frame = new AVFrame
                            {
                                data = data,
                                linesize = linesize,
                                height = sourceSize.Height
                            };

                            var convertedFrame = vfc.Convert(frame);
                            convertedFrame.pts = frameNumber;

                            vse.Encode(convertedFrame);

                            Debug.Log($"frame: {frameNumber}");
                            frameNumber++;
                        }
                    }
                    byte[] endcode = { 0, 0, 1, 0xb7 };
                    fs.Write(endcode, 0, endcode.Length);
                }
                Debug.Log(outputFileName);
            }
            catch (Exception ex)
            {
                Debug.LogException(ex);
            }
        }

        private static byte[] GetBitmapData(Texture2D frameBitmap)
        {
            return frameBitmap.GetRawTextureData();
        }
    }

    public sealed unsafe class H264VideoStreamEncoder : IDisposable
    {
        private readonly Size _frameSize;
        private readonly int _linesizeU;
        private readonly int _linesizeV;
        private readonly int _linesizeY;
        private readonly AVCodec* _pCodec;
        private readonly AVCodecContext* _pCodecContext;
        private readonly Stream _stream;
        private readonly int _uSize;
        private readonly int _ySize;

        public H264VideoStreamEncoder(Stream stream, int fps, Size frameSize)
        {
            _stream = stream;
            _frameSize = frameSize;

            var codecId = AVCodecID.AV_CODEC_ID_H264;
            _pCodec = ffmpeg.avcodec_find_encoder(codecId);
            if (_pCodec == null)
                throw new InvalidOperationException("Codec not found.");

            _pCodecContext = ffmpeg.avcodec_alloc_context3(_pCodec);
            _pCodecContext->bit_rate = 400000;
            _pCodecContext->width = frameSize.Width;
            _pCodecContext->height = frameSize.Height;
            _pCodecContext->time_base = new AVRational { num = 1, den = fps };
            _pCodecContext->gop_size = 10;
            _pCodecContext->max_b_frames = 1;
            _pCodecContext->pix_fmt = AVPixelFormat.AV_PIX_FMT_YUV420P;

            if (codecId == AVCodecID.AV_CODEC_ID_H264)
                ffmpeg.av_opt_set(_pCodecContext->priv_data, "preset", "veryslow", 0);

            ffmpeg.avcodec_open2(_pCodecContext, _pCodec, null).ThrowExceptionIfError();

            _linesizeY = frameSize.Width;
            _linesizeU = frameSize.Width / 2;
            _linesizeV = frameSize.Width / 2;

            _ySize = _linesizeY * frameSize.Height;
            _uSize = _linesizeU * frameSize.Height / 2;
        }

        public void Dispose()
        {
            ffmpeg.avcodec_close(_pCodecContext);
            ffmpeg.av_free(_pCodecContext);
        }

        public void Encode(AVFrame frame)
        {
            if (frame.format != (int)_pCodecContext->pix_fmt)
                throw new ArgumentException("Invalid pixel format.", nameof(frame));
            if (frame.width != _frameSize.Width)
                throw new ArgumentException("Invalid width.", nameof(frame));
            if (frame.height != _frameSize.Height)
                throw new ArgumentException("Invalid height.", nameof(frame));
            if (frame.linesize[0] < _linesizeY)
                throw new ArgumentException("Invalid Y linesize.", nameof(frame));
            if (frame.linesize[1] < _linesizeU)
                throw new ArgumentException("Invalid U linesize.", nameof(frame));
            if (frame.linesize[2] < _linesizeV)
                throw new ArgumentException("Invalid V linesize.", nameof(frame));
            if (frame.data[1] - frame.data[0] < _ySize)
                throw new ArgumentException("Invalid Y data size.", nameof(frame));
            if (frame.data[2] - frame.data[1] < _uSize)
                throw new ArgumentException("Invalid U data size.", nameof(frame));

            var pPacket = ffmpeg.av_packet_alloc();
            try
            {
                int error;
                do
                {
                    ffmpeg.avcodec_send_frame(_pCodecContext, &frame).ThrowExceptionIfError();
                    ffmpeg.av_packet_unref(pPacket);
                    error = ffmpeg.avcodec_receive_packet(_pCodecContext, pPacket);
                } while (error == ffmpeg.AVERROR(ffmpeg.EAGAIN));

                error.ThrowExceptionIfError();

                using var packetStream = new UnmanagedMemoryStream(pPacket->data, pPacket->size);
                packetStream.CopyTo(_stream);
            }
            finally
            {
                ffmpeg.av_packet_free(&pPacket);
            }
        }
    }


  


• C# WinForms, play video using the FFmpeg library

  25 septembre 2020, par Damn Vegetables

  According to web search results, FFmpeg.AutoGen provides video/audio frames with timing data, and I could use them to render the way I want. But I cannot find a simple example for playing a video file on a WinForms window, using FFmpeg.

  


  In the example file, I can see code for initialisation and decoding video frames. How to play those frames smoothly on WinForms ? Should I use some sort of DirectX library ?