VideoFileWriter.WriteAudioFrame - issue with stereo signal (3.8.2 prerelese)

[Barrent]

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• question
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Issue description

Hi,

Adding signal to video works fine if mono is used, but a bug appears when stereo input is used (stereo sound is two times slower and has a lot of distortion).

Here is the code:

            var decoder = new WaveDecoder(@"D:\SoundSample1Sec.wav");
            var stereo = decoder.Decode();
            decoder.Close();

            var mono = Signal.FromArray(stereo.InnerData.Cast<float>().Where((x, i) => i % 2 == 0).ToArray(), 1, stereo.SampleRate);

            var signal = stereo;

            var image = GetImage();
            var writer = new VideoFileWriter
            {
                Height = image.Height,
                Width = image.Width,
                FrameRate = 1,
                FrameSize = signal.Length,
                VideoCodec = VideoCodec.Mpeg4,
                AudioCodec = AudioCodec.Aac
            };

            writer.Open(@"D:\TestVideo.mp4");
            writer.WriteVideoFrame(image);
            writer.WriteAudioFrame(signal);
            writer.Close();

I dug into Accord sources a little bit and found that in method VideoFileWriter.send_audio_frame number of channel isn't taken into account properly. In a row
size_t sampleSize = m_input_audio_sample_size;
sampleSize is assigned to 4 (I think it should be 8 bytes in case of stereo data)
If multiply it by m_input_audio_channels then stereo signal is written to file properly.
Maybe this bug also can be fixed by updating Singal.SampleSize property (it returns 4 bytes for stereo signal).

[nesherhh]

I can confirm, this fix.