uint32_t WaveReader::Read(uint32_t num_samples)
{
int64_t end_position = mPosition + num_samples;
// check read limits
if (mSampleCount <= 0 ||
mPosition >= mSampleCount ||
mPosition >= mReadStartPosition + mReadDuration ||
end_position <= 0 ||
end_position <= mReadStartPosition)
{
// always be positioned num_samples after previous position
Seek(end_position);
return 0;
}
// adjust sample count and seek to start of data if needed
uint32_t first_sample_offset = 0;
uint32_t read_num_samples = num_samples;
if (mPosition < mReadStartPosition) {
first_sample_offset = (uint32_t)(mReadStartPosition - mPosition);
read_num_samples -= first_sample_offset;
Seek(mReadStartPosition);
}
if (end_position > mReadStartPosition + mReadDuration)
read_num_samples -= (uint32_t)(end_position - (mReadStartPosition + mReadDuration));
BMX_ASSERT(read_num_samples > 0);
// read samples
bool have_read = false;
size_t i;
for (i = 0; i < mTracks.size(); i++) {
if (!mTracks[i]->IsEnabled())
continue;
Frame *frame = mTracks[i]->GetFrameBuffer()->CreateFrame();
frame->Grow(read_num_samples * mTracks[i]->GetBlockAlign());
// read samples directly into the frame if there is only 1 track; else read into read buffer
if (!have_read) {
unsigned char *buffer;
if (mTracks.size() == 1) {
buffer = frame->GetBytesAvailable();
} else {
mReadBuffer.Allocate(read_num_samples * mBlockAlign);
buffer = mReadBuffer.GetBytes();
}
uint32_t bytes_read = mInput->Read(buffer, read_num_samples * mBlockAlign);
if (bytes_read < read_num_samples * mBlockAlign) {
log_error("Failed to read %u samples of %u\n",
read_num_samples - bytes_read / mBlockAlign, read_num_samples);
read_num_samples = bytes_read / mBlockAlign;
}
if (mTracks.size() > 1)
mReadBuffer.SetSize(read_num_samples * mBlockAlign);
have_read = true;
}
if (mTracks.size() > 1) {
deinterleave_audio(mReadBuffer.GetBytes(), mReadBuffer.GetSize(),
mQuantizationBits, mChannelCount, (uint16_t)i,
frame->GetBytesAvailable(), frame->GetSizeAvailable());
}
frame->SetSize(read_num_samples * mTracks[i]->GetBlockAlign());
frame->edit_rate = mSamplingRate;
frame->position = mPosition;
frame->track_edit_rate = mSamplingRate;
frame->track_position = mPosition;
frame->request_num_samples = num_samples;
frame->first_sample_offset = first_sample_offset;
frame->num_samples = read_num_samples;
frame->file_position = mDataStartFilePosition + mPosition * mBlockAlign;
mTracks[i]->GetFrameBuffer()->PushFrame(frame);
}
if (have_read)
mPosition += read_num_samples;
// always be positioned num_samples after previous position
if (mPosition < end_position)
Seek(end_position);
return read_num_samples;
}
