BakaMusicPlayer/Bmp.Core/FFMpeg/CsCorePorts/FFMpegWrap/FfmpegDecoder.cs


using System.Runtime.InteropServices;
using Bmp.Core.FFMpeg.CsCoreExt;

namespace Bmp.Core.FFMpeg.CsCorePorts.FFMpegWrap;

/// <summary>
///     Generic FFmpeg based decoder.
/// </summary>
/// <remarks>
///     The <see cref="FfmpegDecoder" /> uses the FFmpeg libraries to decode audio files.
///     In order to make sure that the FFmpeg libraries are compatible with the <see cref="FfmpegDecoder" />,
///     use the binaries shipped with the CSCore.Ffmpeg project.
///     If a custom build is necessary, use the FFmpeg source code, from the CSCore git repository
///     (https://github.com/filoe/cscore).
/// </remarks>
public class FfmpegDecoder : IWaveSource
{
    // BmpMod: Add `AttachedPic` and `BitPerRawSample`

    public FFMpegAttachedPicCollection? AttachedPics => _formatContext == null ? null : new FFMpegAttachedPicCollection(_formatContext.FormatContext);

    public unsafe int? BitPerRawSample => _formatContext != null ? _formatContext.SelectedStream.Stream.codec->bits_per_raw_sample : null;
    public unsafe long? StreamBitPerSecond => _formatContext != null ? _formatContext.SelectedStream.Stream.codec->bit_rate : null;
    public long? FileBitPerSecond => _formatContext?.FormatContext.bit_rate;

    public unsafe string? FileFormat
    {
        get
        {
            if (_formatContext == null) return null;

            var codec = Marshal.PtrToStringUTF8((nint)_formatContext.SelectedStream.Stream.codec->codec->long_name);
            var container = Marshal.PtrToStringUTF8((nint)_formatContext.FormatContext.iformat->name);

            return $"{codec} @ {container}";
        }
    }

    // Orig

    private readonly object _lockObject = new object();
    private readonly Uri _uri;
    private FfmpegStream? _ffmpegStream;
    private AvFormatContext? _formatContext;
    private bool _disposeStream = false;

    private byte[] _overflowBuffer = Array.Empty<byte>();
    private int _overflowCount;
    private int _overflowOffset;
    private long _position;
    private Stream? _stream;

    /// <summary>
    /// Gets a dictionary with found metadata.
    /// </summary>
    public Dictionary<string, string> Metadata
    {
        get
        {
            if (_formatContext == null)
                return new Dictionary<string, string>();
            return _formatContext.Metadata;
        }
    }

    /// <summary>
    ///     Initializes a new instance of the <see cref="FfmpegDecoder" /> class based on a specified filename or url.
    /// </summary>
    /// <param name="url">A url containing a filename or web url. </param>
    /// <exception cref="FfmpegException">
    ///     Any ffmpeg error.
    /// </exception>
    /// <exception cref="NotSupportedException">
    ///     DBL format is not supported.
    ///     or
    ///     Audio Sample Format not supported.
    /// </exception>
    /// <exception cref="ArgumentNullException">uri</exception>
    public FfmpegDecoder(string url)
    {
        const int invalidArgument = unchecked((int)0xffffffea);

        _uri = new Uri(url);
        try
        {
            _formatContext = new AvFormatContext(url);
            Initialize();
        }
        catch (FfmpegException ex)
        {
            if (ex.ErrorCode == invalidArgument && "avformat_open_input".Equals(ex.Function, StringComparison.OrdinalIgnoreCase))
            {
                if (!TryInitializeWithFileAsStream(url))
                    throw;
            }
            else
            {
                throw;
            }
        }
    }

    /// <summary>
    ///     Initializes a new instance of the <see cref="FfmpegDecoder" /> class based on a <see cref="Stream" />.
    /// </summary>
    /// <param name="stream">The stream.</param>
    /// <exception cref="FfmpegException">Any ffmpeg error.</exception>
    /// <exception cref="ArgumentNullException">stream</exception>
    /// <exception cref="ArgumentException">Stream is not readable.</exception>
    /// <exception cref="OutOfMemoryException">Could not allocate FormatContext.</exception>
    /// <exception cref="NotSupportedException">
    ///     DBL format is not supported.
    ///     or
    ///     Audio Sample Format not supported.
    /// </exception>
    public FfmpegDecoder(Stream stream)
    {
        if (stream == null)
            throw new ArgumentNullException("stream");

        InitializeWithStream(stream, false);
    }

    /// <summary>
    ///     Reads a sequence of bytes from the <see cref="FfmpegDecoder" /> and advances the position within the
    ///     stream by the
    ///     number of bytes read.
    /// </summary>
    /// <param name="buffer">
    ///     An array of bytes. When this method returns, the <paramref name="buffer" /> contains the specified
    ///     array of bytes with the values between <paramref name="offset" /> and (<paramref name="offset" /> +
    ///     <paramref name="count" /> - 1) replaced by the bytes read from the current source.
    /// </param>
    /// <param name="offset">
    ///     The zero-based offset in the <paramref name="buffer" /> at which to begin storing the data
    ///     read from the current stream.
    /// </param>
    /// <param name="count">The maximum number of bytes to read from the current source.</param>
    /// <returns>The total number of bytes read into the buffer.</returns>
    public int Read(byte[] buffer, int offset, int count)
    {
        var read = 0;
        count -= count % WaveFormat.BlockAlign;
        var fetchedOverflows = GetOverflows(buffer, ref offset, count);
        read += fetchedOverflows;

        while (read < count)
        {
            long packetPosition;
            int bufferLength;
            lock (_lockObject)
            {
                using (var frame = new AvFrame(_formatContext))
                {
                    double seconds;
                    bufferLength = frame.ReadNextFrame(out seconds, ref _overflowBuffer);
                    packetPosition = this.GetRawElements(TimeSpan.FromSeconds(seconds));
                }
            }
            if (bufferLength <= 0)
            {
                //if (_uri != null && !_uri.IsFile)
                //{
                //    //webstream: don't exit, maybe the connection was lost -> give it a try to recover
                //    Thread.Sleep(10);
                //}
                //else
                break; //no webstream -> exit
            }
            var bytesToCopy = Math.Min(count - read, bufferLength);
            Array.Copy(_overflowBuffer, 0, buffer, offset, bytesToCopy);
            read += bytesToCopy;
            offset += bytesToCopy;

            _overflowCount = bufferLength > bytesToCopy ? bufferLength - bytesToCopy : 0;
            _overflowOffset = bufferLength > bytesToCopy ? bytesToCopy : 0;

            _position = packetPosition + read - fetchedOverflows;
        }

        if (fetchedOverflows == read)
        {
            //no new packet was decoded -> add the read bytes to the position
            _position += read;
        }

        return read;
    }

    /// <summary>
    ///     Gets a value indicating whether the <see cref="FfmpegDecoder" /> supports seeking.
    /// </summary>
    public bool CanSeek
    {
        get
        {
            if (_formatContext == null)
                return false;
            return _formatContext.CanSeek;
        }
    }

    /// <summary>
    ///     Gets the <see cref="IAudioSource.WaveFormat" /> of the waveform-audio data.
    /// </summary>
    public WaveFormat WaveFormat { get; private set; }

    /// <summary>
    ///     Gets or sets the current position in bytes.
    /// </summary>
    public long Position
    {
        get { return _position; }
        set { SeekPosition(value); }
    }

    /// <summary>
    ///     Gets the length of the waveform-audio data in bytes.
    /// </summary>
    public long Length
    {
        get
        {
            if (_formatContext == null || _formatContext.SelectedStream == null)
                return 0;
            return this.GetRawElements(TimeSpan.FromSeconds(_formatContext.LengthInSeconds));
        }
    }

    /// <summary>
    ///     Releases all allocated resources used by the <see cref="FfmpegDecoder" />.
    /// </summary>
    public void Dispose()
    {
        Dispose(true);
    }

    /// <summary>
    /// Releases unmanaged and - optionally - managed resources.
    /// </summary>
    /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
    protected void Dispose(bool disposing)
    {
        GC.SuppressFinalize(this);

        if (disposing)
        {
            if (_disposeStream && _stream != null)
            {
                _stream.Dispose();
                _stream = null;
            }

            if (_formatContext != null)
            {
                _formatContext.Dispose();
                _formatContext = null;
            }

            if (_ffmpegStream != null)
            {
                _ffmpegStream.Dispose();
                _ffmpegStream = null;
            }
        }
    }

    private unsafe void Initialize()
    {
        if (_formatContext == null) throw new InvalidOperationException();
        WaveFormat = _formatContext.SelectedStream.GetSuggestedWaveFormat();
    }

    private void InitializeWithStream(Stream stream, bool disposeStream)
    {
        _stream = stream;
        _disposeStream = disposeStream;

        _ffmpegStream = new FfmpegStream(stream, false);
        _formatContext = new AvFormatContext(_ffmpegStream);
        Initialize();
    }

    private bool TryInitializeWithFileAsStream(string filename)
    {
        if (!File.Exists(filename))
            return false;

        Stream stream = null;
        try
        {
            stream = File.OpenRead(filename);
            InitializeWithStream(stream, true);
            return true;
        }
        catch (Exception)
        {
            if (stream != null)
            {
                stream.Dispose();
            }
            return false;
        }
    }

    /// <summary>
    ///     Finalizes an instance of the <see cref="FfmpegDecoder" /> class.
    /// </summary>
    ~FfmpegDecoder()
    {
        Dispose(false);
    }

    private void SeekPosition(long position)
    {
        //https://ffmpeg.org/doxygen/trunk/seek-test_8c-source.html
        var seconds = this.GetMilliseconds(position) / 1000.0;
        lock (_lockObject)
        {
            _formatContext.SeekFile(seconds);

            _position = position;
            _overflowCount = 0;
            _overflowOffset = 0;
        }
    }

    private int GetOverflows(byte[] buffer, ref int offset, int count)
    {
        if (_overflowCount != 0 && _overflowBuffer != null && count > 0)
        {
            var bytesToCopy = Math.Min(count, _overflowCount);
            Array.Copy(_overflowBuffer, _overflowOffset, buffer, offset, bytesToCopy);

            _overflowCount -= bytesToCopy;
            _overflowOffset += bytesToCopy;
            offset += bytesToCopy;
            return bytesToCopy;
        }
        return 0;
    }
}