Specify number of channels in the data passed to SoundAssetWriter, and pad channels...

[libdcp.git] / src / sound_asset_writer.cc

diff --git a/src/sound_asset_writer.cc b/src/sound_asset_writer.cc
index a0414aba3e5a3d2f486e09ff3c06d42bbc68ecdf..f789eb3b9a6b18199cdb2c61d2ee6959c47e7425 100644 (file)
--- a/src/sound_asset_writer.cc
+++ b/src/sound_asset_writer.cc
@@ -200,29 +200,30 @@ LIBDCP_ENABLE_WARNINGS
 
 
 void
-SoundAssetWriter::write (float const * const * data, int frames)
+SoundAssetWriter::write(float const * const * data, int data_channels, int frames)
 {
        DCP_ASSERT (!_finalized);
        DCP_ASSERT (frames > 0);
 
+       auto const asset_channels = _asset->channels();
+       DCP_ASSERT (data_channels <= asset_channels);
+
        static float const clip = 1.0f - (1.0f / pow (2, 23));
 
        if (!_started) {
                start ();
        }
 
-       int const ch = _asset->channels ();
-
        for (int i = 0; i < frames; ++i) {
 
                byte_t* out = _state->frame_buffer.Data() + _frame_buffer_offset;
 
-               /* Write one sample per channel */
-               for (int j = 0; j < ch; ++j) {
+               /* Write one sample per asset channel */
+               for (int j = 0; j < asset_channels; ++j) {
                        int32_t s = 0;
                        if (j == 13 && _sync) {
                                s = _fsk.get();
-                       } else {
+                       } else if (j < data_channels) {
                                /* Convert sample to 24-bit int, clipping if necessary. */
                                float x = data[j][i];
                                if (x > clip) {
@@ -236,7 +237,7 @@ SoundAssetWriter::write (float const * const * data, int frames)
                        *out++ = (s & 0xff00) >> 8;
                        *out++ = (s & 0xff0000) >> 16;
                }
-               _frame_buffer_offset += 3 * ch;
+               _frame_buffer_offset += 3 * asset_channels;
 
                DCP_ASSERT (_frame_buffer_offset <= int(_state->frame_buffer.Capacity()));