public IEnumerable <BitmapStream> GetImagesFromMedia(string inputPath, int frameCount, CancellationToken cancellationToken, Action <string> log = null, bool autoToneMapHDR = true)
{
var mediaInfo = GetMediaInfo(inputPath, cancellationToken, log);
log?.Invoke("Reading images from FFmpeg...");
var fps = frameCount / mediaInfo.Duration.TotalSeconds;
var fpsFilter = $"fps={fps.ToInvariantString()}";
// Note: tone mapping algorithms have been tested (*cough* *cough* on the Interstellar movie only =°)
// and compared to the SDR reference barcode, hable seems to give the closest result.
// Warning: this is very slow!
// https://web.archive.org/web/20190722004804/https://stevens.li/guides/video/converting-hdr-to-sdr-with-ffmpeg/
var hdrToSdrFilter = "zscale=transfer=linear:npl=100,format=gbrpf32le,zscale=primaries=bt709,tonemap=tonemap=hable,zscale=transfer=bt709:matrix=bt709:range=tv,format=yuv420p";
var vfilters = new List <string> {
fpsFilter
};
if (mediaInfo.IsHDR && autoToneMapHDR)
{
log?.Invoke("HDR video detected. Adding tone mapping filter.");
vfilters.Add(hdrToSdrFilter);
}
// Output a raw stream of bitmap images taken at the specified frequency
var args = $"-i \"{inputPath}\" -vf \"{string.Join(",", vfilters)}\" -c:v bmp -f rawvideo -an -";
log?.Invoke($"FFmpeg arguments: {args}");
var process = StartFfmpegInstance(args, redirectError: log != null);
if (log != null)
{
process.ErrorDataReceived += (s, e) => log(e.Data);
process.BeginErrorReadLine();
}
IEnumerable <BitmapStream> GetLazyStream()
{
using (cancellationToken.Register(() => TryKill(process)))
using (var reader = new BinaryReader(process.StandardOutput.BaseStream))
{
while (BitmapStream.TryCreate(reader, out var bitmapStream, cancellationToken))
{
yield return(bitmapStream);
}
}
}
return(GetLazyStream());
}
public static bool TryCreate(BinaryReader reader, out BitmapStream bitmapStream, CancellationToken cancellationToken)
{
try
{
// https://en.wikipedia.org/wiki/BMP_file_format
var magicNumber = reader.ReadBytes(2);
if (magicNumber.Length != 2)
{
bitmapStream = null;
return(false);
}
if (magicNumber[0] != 0x42 || magicNumber[1] != 0x4D)
{
throw new InvalidDataException();
}
var bmpSizeBytes = reader.ReadBytes(4);
var bmpSize = BitConverter.ToInt32(bmpSizeBytes, 0);
var remainingDataLength = bmpSize - bmpSizeBytes.Length - magicNumber.Length;
var remainingData = reader.ReadBytes(remainingDataLength);
var ms = new MemoryStream();
ms.Write(magicNumber, 0, magicNumber.Length);
ms.Write(bmpSizeBytes, 0, bmpSizeBytes.Length);
ms.Write(remainingData, 0, remainingData.Length);
ms.Position = 0;
bitmapStream = new BitmapStream(ms);
return(true);
}
catch (Exception)
{
if (cancellationToken.IsCancellationRequested)
{
cancellationToken.ThrowIfCancellationRequested();
throw new OperationCanceledException();
}
else
{
throw;
}
}
}
public override void Flush()
{
BitmapStream?.Flush();
DataA?.Flush();
DataB?.Flush();
}
