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MP3File: Fix stereo playback on samd AudioOut 

There were several problems with the way this worked -- the read_count
approach was too complicated and I made a mistake "simplifying" it from
WaveFile.  And when the right channel was returned, it was off by 1 byte,
making it into static.

Instead, directly track which is the "other" channel that has data
available, and by using the right data type make the "+ channel"
arithmetic give the right result.

This requires a double cast (int16_t*)(void*) due to an alignment warning;
the alignment is now ensured manually, but the compiler doesn't make the
necessary inference that the low address bit must be clear.
This commit is contained in:
Jeff Epler 2019-12-12 08:44:15 -06:00
parent 8c841af946
commit 1cdac3f16a
2 changed files with 30 additions and 22 deletions
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46
shared-module/audiomp3/MP3File.c
View File

@ -151,10 +151,13 @@ void common_hal_audiomp3_mp3file_construct(audiomp3_mp3file_obj_t* self,
self->channel_count = fi.nChans;
self->frame_buffer_size = fi.outputSamps*sizeof(int16_t);
if ((intptr_t)buffer & 1) {
buffer += 1; buffer_size -= 1;
}
if (buffer_size >= 2 * self->frame_buffer_size) {
self->len = buffer_size / 2 / self->frame_buffer_size * self->frame_buffer_size;
self->buffers[0] = buffer;
self->buffers[1] = buffer + self->len;
self->buffers[0] = (int16_t*)(void*)buffer;
self->buffers[1] = (int16_t*)(void*)buffer + self->len;
} else {
self->len = 2 * self->frame_buffer_size;
self->buffers[0] = m_malloc(self->len, false);
@ -218,6 +221,7 @@ void audiomp3_mp3file_reset_buffer(audiomp3_mp3file_obj_t* self,
f_lseek(&self->file->fp, 0);
self->inbuf_offset = self->inbuf_length;
self->eof = 0;
self->other_channel = -1;
mp3file_update_inbuf(self);
mp3file_find_sync_word(self);
}
@ -234,26 +238,30 @@ audioio_get_buffer_result_t audiomp3_mp3file_get_buffer(audiomp3_mp3file_obj_t*
channel = 0;
}
uint16_t channel_read_count = self->channel_read_count[channel]++;
bool need_more_data = self->read_count++ == channel_read_count;
*bufptr = self->buffers[self->buffer_index] + channel;
*bufptr = (uint8_t*)(self->buffers[self->buffer_index] + channel);
*buffer_length = self->frame_buffer_size;
if (need_more_data) {
self->buffer_index = !self->buffer_index;
int16_t *buffer = (int16_t *)(void *)self->buffers[self->buffer_index];
if (channel == self->other_channel) {
*bufptr = (uint8_t*)(self->buffers[self->other_buffer_index] + channel);
self->other_channel = -1;
return GET_BUFFER_MORE_DATA;
}
if (!mp3file_find_sync_word(self)) {
return self->eof ? GET_BUFFER_DONE : GET_BUFFER_ERROR;
}
int bytes_left = BYTES_LEFT(self);
uint8_t *inbuf = READ_PTR(self);
int err = MP3Decode(self->decoder, &inbuf, &bytes_left, buffer, 0);
CONSUME(self, BYTES_LEFT(self) - bytes_left);
if (err) {
return GET_BUFFER_DONE;
}
self->other_channel = 1-channel;
self->other_buffer_index = self->buffer_index;
self->buffer_index = !self->buffer_index;
int16_t *buffer = (int16_t *)(void *)self->buffers[self->buffer_index];
if (!mp3file_find_sync_word(self)) {
return self->eof ? GET_BUFFER_DONE : GET_BUFFER_ERROR;
}
int bytes_left = BYTES_LEFT(self);
uint8_t *inbuf = READ_PTR(self);
int err = MP3Decode(self->decoder, &inbuf, &bytes_left, buffer, 0);
CONSUME(self, BYTES_LEFT(self) - bytes_left);
if (err) {
return GET_BUFFER_DONE;
}
return GET_BUFFER_MORE_DATA;

6
shared-module/audiomp3/MP3File.h
View File

@ -39,7 +39,7 @@ typedef struct {
uint8_t* inbuf;
uint32_t inbuf_length;
uint32_t inbuf_offset;
uint8_t* buffers[2];
int16_t* buffers[2];
uint32_t len;
uint32_t frame_buffer_size;
@ -50,8 +50,8 @@ typedef struct {
uint8_t channel_count;
bool eof;
uint16_t read_count;
uint16_t channel_read_count[2];
int8_t other_channel;
int8_t other_buffer_index;
} audiomp3_mp3file_obj_t;
// These are not available from Python because it may be called in an interrupt.