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• How to decode mp3 to raw sample data for FFMpeg using FFMediaToolkit

  28 décembre 2022, par Lee

  My objective is to create a video slideshow with audio using a database as the source. The final implementation video and audio inputs need to be memory streams or byte arrays, not a file system path. The sample code is file based for portability. It's just trying to read a file based mp3 then write it to the output.

  


  I've tried a few FFMpeg wrappers and I'm open to alternatives. This code is using FFMediaToolkit. The video portion of the code works. It's the audio that I can't get to work.

  


  The input is described as "A 2D jagged array of multi-channel sample data with NumChannels rows and NumSamples columns." The datatype is float[][].

  


  My mp3 source is mono. I'm using NAudio.Wave to decode the mp3. It is then split into chunks equal to the frame size for the sample rate. It is then converted into the jagged float with the data on channel 0.

  


  The FFMpeg decoder displays a long list of "buffer underflow" and "packet too large, ignoring buffer limits to mux it". C# returns "Specified argument was out of the range of valid values." The offending line of code being "file.Audio.AddFrame(frameAudio)".

  


  The source is 16 bit samples. The PCM_S16BE codec is the only one that I could get to accept 16 bit sample format. I could only get the MP3 encoder to work with "Signed 32-bit integer (planar)" as the sample format. I'm not certain if the source data needs to be converted from 16 to 32 bit to use the codec.

  


  `

  


  using FFMediaToolkit;
using FFMediaToolkit.Decoding;
using FFMediaToolkit.Encoding;
using FFMediaToolkit.Graphics;
using System;
using System.Collections.Generic;
using System.Drawing.Imaging;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using FFMediaToolkit.Audio;
using NAudio.Wave;
using FFmpeg.AutoGen;

    internal class FFMediaToolkitTest
    {
        const int frameRate = 30;
        const int vWidth = 1920;
        const int vHeight = 1080;
        const int aSampleRate = 24_000; // source sample rate
        //const int aSampleRate = 44_100;
        const int aSamplesPerFrame = aSampleRate / frameRate;
        const int aBitRate = 32_000;
        const string dirInput = @"D:\Websites\Vocabulary\Videos\source\";
        const string pathOutput = @"D:\Websites\Vocabulary\Videos\example.mpg";

        public FFMediaToolkitTest()
        {
            try
            {
                FFmpegLoader.FFmpegPath = ".";  //  FFMpeg  DLLs in root project directory
                var settings = new VideoEncoderSettings(width: vWidth, height: vHeight, framerate: frameRate, codec: VideoCodec.H264);
                settings.EncoderPreset = EncoderPreset.Fast;
                settings.CRF = 17;

                //var settingsAudio = new AudioEncoderSettings(aSampleRate, 1, (AudioCodec)AVCodecID.AV_CODEC_ID_PCM_S16BE);  // Won't run with low bitrate.
                var settingsAudio = new AudioEncoderSettings(aSampleRate, 1, AudioCodec.MP3); // mpg runs with SampleFormat.SignedDWordP
                settingsAudio.Bitrate = aBitRate;
                //settingsAudio.SamplesPerFrame = aSamplesPerFrame;
                settingsAudio.SampleFormat = SampleFormat.SignedDWordP;

                using (var file = MediaBuilder.CreateContainer(pathOutput).WithVideo(settings).WithAudio(settingsAudio).Create())
                {
                    var files = Directory.GetFiles(dirInput, "*.jpg");
                    foreach (var inputFile in files)
                    {
                        Console.WriteLine(inputFile);
                        var binInputFile = File.ReadAllBytes(inputFile);
                        var memInput = new MemoryStream(binInputFile);
                        var bitmap = Bitmap.FromStream(memInput) as Bitmap;
                        var rect = new System.Drawing.Rectangle(System.Drawing.Point.Empty, bitmap.Size);
                        var bitLock = bitmap.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
                        var bitmapData = ImageData.FromPointer(bitLock.Scan0, ImagePixelFormat.Bgr24, bitmap.Size);

                        for (int i = 0; i < 60; i++)
                            file.Video.AddFrame(bitmapData); 
                        bitmap.UnlockBits(bitLock);
                    }

                    var mp3files = Directory.GetFiles(dirInput, "*.mp3");
                    foreach (var inputFile in mp3files)
                    {
                        Console.WriteLine(inputFile);
                        var binInputFile = File.ReadAllBytes(inputFile);
                        var memInput = new MemoryStream(binInputFile);

                        foreach (float[][] frameAudio in GetFrames(memInput))
                        {
                            file.Audio.AddFrame(frameAudio); // encode the frame
                        }
                    }
                    //Console.WriteLine(file.Audio.CurrentDuration);
                    Console.WriteLine(file.Video.CurrentDuration);
                    Console.WriteLine(file.Video.Configuration);
                }
            }
            catch (Exception e)
            {
                Vocab.LogError("FFMediaToolkitTest", e.StackTrace + " " + e.Message);
                Console.WriteLine(e.StackTrace + " " + e.Message);
            }

            Console.WriteLine();
            Console.WriteLine("Done");
            Console.ReadLine();
        }


        public static List GetFrames(MemoryStream mp3stream)
        {
            List output = new List();
            
            int frameCount = 0;

            NAudio.Wave.StreamMediaFoundationReader smfReader = new StreamMediaFoundationReader(mp3stream);
            Console.WriteLine(smfReader.WaveFormat);
            Console.WriteLine(smfReader.WaveFormat.AverageBytesPerSecond); //48000
            Console.WriteLine(smfReader.WaveFormat.BitsPerSample);  // 16
            Console.WriteLine(smfReader.WaveFormat.Channels);  // 1 
            Console.WriteLine(smfReader.WaveFormat.SampleRate);     //24000

            Console.WriteLine("PCM bytes: " + smfReader.Length);
            Console.WriteLine("Total Time: " + smfReader.TotalTime);

            int samplesPerFrame = smfReader.WaveFormat.SampleRate / frameRate;
            int bytesPerFrame = samplesPerFrame * smfReader.WaveFormat.BitsPerSample / 8;
            byte[] byteBuffer = new byte[bytesPerFrame];

            while (smfReader.Read(byteBuffer, 0, bytesPerFrame) != 0)
            {
                float[][] buffer = Convert16BitToFloat(byteBuffer);
                output.Add(buffer);
                frameCount++;
            }
            return output;
        }

        public static float[][] Convert16BitToFloat(byte[] input)
        {
            // Only works with single channel data
            int inputSamples = input.Length / 2;
            float[][] output = new float[1][]; 
            output[0] = new float[inputSamples];
            int outputIndex = 0;
            for (int n = 0; n < inputSamples; n++)
            {
                short sample = BitConverter.ToInt16(input, n * 2);
                output[0][outputIndex++] = sample / 32768f;
            }
            return output;
        }

    }




  


  `

  


  I've tried multiple codecs with various settings. I couldn't get any of the codecs to accept a mp4 output file extension. FFMpeg will run but error out with mpg as the output file.

  


• how to add duration to mjpeg or how to make mjpeg faster

  10 octobre 2014, par n2v2rda2

  i have ip-cam mjpeg that i made and it have total 240 frames

  encode souce is
  ffmpeg.exe -framerate 25 -i c :\%06d.jpg\ -s 1920x1080 -qscale 1 -vcodec mjpeg -r 25 C :\result.mjpg -y

  now i want to play result.mjpg by mjpeg player i made

  my problem
  
  1. i can't get mjpeg's play time or duration time
  
  
  
  2. playing is slower then other movie player so i want to sync it and play more faster

  below is ffprobe result

  Input #0, mjpeg, from 'result.mjpg':
  
  Duration: N/A, bitrate: N/A
  
  Stream #0:0: Video: mjpeg, yuvj444p(pc, bt470bg), 1920x1080, 25 tbr, 1200k tbn, 25 tbc

  below is result added -show_frame

  [FRAME]
  
  media_type=video
  
  key_frame=1
  
  pkt_pts=720000
  
  pkt_pts_time=0.600000
  
  pkt_dts=720000
  
  pkt_dts_time=0.600000
  
  best_effort_timestamp=720000
  
  best_effort_timestamp_time=0.600000
  
  pkt_duration=48000
  
  pkt_duration_time=0.040000
  
  pkt_pos=4731406
  
  pkt_size=313289
  
  width=1920
  
  height=1080
  
  pix_fmt=yuvj444p
  
  sample_aspect_ratio=333:320
  
  pict_type=I
  
  coded_picture_number=0
  
  display_picture_number=0
  
  interlaced_frame=0
  
  top_field_first=0
  
  repeat_pict=0
  
  [/FRAME]

  ffprobe show me there are Duration : N/A, bitrate : N/A

  how do i set Duration and bitrate
  is there any encode-option i have to set ?

  when i decode mjpeg like below

  i can’t get duration just 0

  AVFormatContext*  pFC;
  
  int               ret;
  
  
  
  pFC = avformat_alloc_context();
  
  
  
  ret  = avformat_open_input(&pFC, filename, NULL, NULL);
  
  if (ret < 0) {
  
      // fail .
  
  }
  
  
  
  ret  = avformat_find_stream_info(pFC, NULL);
  
  if (ret < 0) {
  
      // fail
  
  }
  
  printf("duration %ld", pFC->duration);   <----- only 0

• ffmpeg - creating segments of equivalent duration

  13 octobre 2014, par Code_Ed_Student

  I am testing out segment to split a video into segments of 10 seconds each, but I’m noticing some unusual results. In particular, some of the segments generated have varying lengths from 5 seconds to 11 seconds. I’ve tried playing around with segment_time_delta and force_key_frames to make the segments as close to 10 seconds as possible, but it doesn’t seem to be working out so well. How could I make all segments the same duration ?

  ffmpeg -i input.mp4 -force_key_frames 10,20,30,40,50,60,70,80,90,100,110,120 -c copy -map 0 -segment_time 10 -f segment output%01d.mp4

  Results :

  My_vid.mp4 – total duration - 00:02:08
  
  Output1.mp4 00:00:07
  
  Output2.mp4 00:00:07
  
  Output3.mp4 00:00:08
  
  Output4.mp4 00:00:08
  
  Output5.mp4 00:00:09
  
  Output6.mp4 00:00:09
  
  Output7.mp4 00:00:10
  
  Output8.mp4 00:00:10
  
  Output9.mp4 00:00:10
  
  Output10.mp4 00:00:11
  
  Output11.mp4  00:00:11
  
  Output12.mp4 00:00:11
  
  Output12.mp4 00:00:13