private void ConvertAudioSample(ref WaveDataType input, IntPtr sample)
{
int ret;
IntPtr swr = AV.swr_alloc_set_opts(IntPtr.Zero,
AV.av_get_default_channel_layout(codecCtx.channels),
AV.AVSampleFormat.AV_SAMPLE_FMT_S16,
codecCtx.sample_rate,
AV.av_get_default_channel_layout(codecCtx.channels),
codecCtx.sample_fmt,
codecCtx.sample_rate,
0,
IntPtr.Zero);
ret = AV.swr_init(swr);
int needed_buf_size = AV.av_samples_get_buffer_size(IntPtr.Zero,
codecCtx.channels,
input.nb_samples,
AV.AVSampleFormat.AV_SAMPLE_FMT_S16, 0);
IntPtr pOutput = Marshal.AllocCoTaskMem(needed_buf_size);
IntPtr ppOutput = Marshal.AllocCoTaskMem(Marshal.SizeOf(pOutput));
Marshal.WriteIntPtr(ppOutput, pOutput);
int len = AV.swr_convert(swr, ppOutput, input.nb_samples, sample, input.nb_samples);
int output_len = len * 2 * AV.av_get_bytes_per_sample(AV.AVSampleFormat.AV_SAMPLE_FMT_S16);
input.managedData = new byte[output_len];
Marshal.Copy(pOutput, input.managedData, 0, output_len);
Marshal.FreeCoTaskMem(pOutput);
Marshal.FreeCoTaskMem(ppOutput);
IntPtr ppSwr = Marshal.AllocCoTaskMem(Marshal.SizeOf(swr));
Marshal.WriteIntPtr(ppSwr, swr);
AV.swr_free(ppSwr);
Marshal.FreeCoTaskMem(ppSwr);
input.bit_per_sample = AV.av_get_bits_per_sample_fmt(AV.AVSampleFormat.AV_SAMPLE_FMT_S16);
input.channel = codecCtx.channels;
input.fmt = AV.AVSampleFormat.AV_SAMPLE_FMT_S16;
input.size = needed_buf_size;
}