/// <summary>
/// Transmit data from current video frame of a <see cref="DecodeContext"/> to a buffer.
/// The buffer holds data for a <see cref="Texture2D"/>. It must have enough capacity to hold the data from a buffer with specified width and height, and format <see cref="SurfaceFormat.Color"/>.
/// </summary>
/// <param name="context">The <see cref="DecodeContext"/> </param>
/// <param name="textureWidth">Width of the texture.</param>
/// <param name="textureHeight">Height of the texture.</param>
/// <param name="buffer">The data buffer.</param>
/// <returns><see langword="true"/> if all successful, otherwise <see langword="false"/>.</returns>
/// <seealso cref="RequiredPixelFormat"/>
internal static bool TransmitVideoFrame([NotNull] DecodeContext context, int textureWidth, int textureHeight, [NotNull] uint[] buffer)
{
Trace.Assert(textureWidth > 0 && textureHeight > 0);
var videoContext = context.VideoContext;
if (videoContext == null)
{
return(false);
}
// Fetch the latest decoded frame.
// You should use a synchronizing mechanism to avoid race condition. See DecodeContext.VideoFrameTransmissionLock.
var videoFrame = context.FetchAvailableVideoFrame();
if (videoFrame == null)
{
return(false);
}
// Here we use the function in FFmpeg to calculate it for us.
// Note the pixel format parameter. We assume that the texture uses the same format.
var requiredBufferSize = ffmpeg.av_image_get_buffer_size(RequiredPixelFormat, textureWidth, textureHeight, 0);
if (buffer.Length * sizeof(uint) < requiredBufferSize)
{
return(false);
}
// Get the SWS context.
var scaleContext = videoContext.GetSuitableScaleContext(textureWidth, textureHeight);
// The type conversion here provided by FFmpeg.AutoGen is invalid, so we have to write a little code...
fixed(uint *pBuffer = buffer)
{
var dstData = new[] { (byte *)pBuffer };
var dstStride = new[] { textureWidth *sizeof(uint) };
// Perform scaling (if needed) and pixel format conversion (if needed), and copy the data to our buffer.
// Thanks @Slow for pointing out the return value of sws_scale.
// This contributes to the correct version of Verify() method. I should have read the docs more carefully.
Verify(ffmpeg.sws_scale(scaleContext, videoFrame->data, videoFrame->linesize, 0, videoContext.CodecContext->height, dstData, dstStride));
}
return(true);
}
