diff options
Diffstat (limited to 'lib/rbcodec/codecs/libm4a/m4a.c')
| -rw-r--r-- | lib/rbcodec/codecs/libm4a/m4a.c | 148 |
1 files changed, 96 insertions, 52 deletions
diff --git a/lib/rbcodec/codecs/libm4a/m4a.c b/lib/rbcodec/codecs/libm4a/m4a.c index 5fe778ac03..b967e15e7a 100644 --- a/lib/rbcodec/codecs/libm4a/m4a.c +++ b/lib/rbcodec/codecs/libm4a/m4a.c @@ -23,6 +23,13 @@ #include <inttypes.h> #include "m4a.h" +#undef DEBUGF +#if defined(DEBUG) +#define DEBUGF stream->ci->debugf +#else +#define DEBUGF(...) +#endif + /* Implementation of the stream.h functions used by libalac */ #define _Swap32(v) do { \ @@ -127,76 +134,113 @@ int m4a_check_sample_offset(demux_res_t *demux_res, uint32_t frame, uint32_t *st return demux_res->lookup_table[i].offset; } -/* Find the exact or preceding frame in lookup_table[]. Return both frame - * and byte position of this match. */ -static void gather_offset(demux_res_t *demux_res, uint32_t *frame, uint32_t *offset) -{ - uint32_t i = 0; - for (i=0; i<demux_res->num_lookup_table; ++i) - { - if (demux_res->lookup_table[i].offset == 0) - break; - if (demux_res->lookup_table[i].sample > *frame) - break; - } - i = (i>0) ? i-1 : 0; /* We want the last chunk _before_ *frame. */ - *frame = demux_res->lookup_table[i].sample; - *offset = demux_res->lookup_table[i].offset; -} - /* Seek to desired sound sample location. Return 1 on success (and modify - * sound_samples_done and current_sample), 0 if failed. - * - * Find the sample (=frame) that contains the given sound sample, find a best - * fit for this sample in the lookup_table[], seek to the byte position. */ + * sound_samples_done and current_sample), 0 if failed. */ unsigned int m4a_seek(demux_res_t* demux_res, stream_t* stream, uint32_t sound_sample_loc, uint32_t* sound_samples_done, int* current_sample) { - uint32_t i = 0; - uint32_t tmp_var, tmp_cnt, tmp_dur; - uint32_t new_sample = 0; /* Holds the amount of chunks/frames. */ - uint32_t new_sound_sample = 0; /* Sums up total amount of samples. */ - uint32_t new_pos; /* Holds the desired chunk/frame index. */ - - /* First check we have the appropriate metadata - we should always - * have it. - */ + uint32_t i, sample_i, sound_sample_i; + uint32_t time, time_cnt, time_dur; + uint32_t chunk, chunk_first_sample; + uint32_t offset; + time_to_sample_t *tts_tab = demux_res->time_to_sample; + sample_offset_t *tco_tab = demux_res->lookup_table; + uint32_t *tsz_tab = demux_res->sample_byte_sizes; + + /* First check we have the required metadata - we should always have it. */ if (!demux_res->num_time_to_samples || !demux_res->num_sample_byte_sizes) - { - return 0; + { + return 0; } - /* Find the destination block from time_to_sample array */ - time_to_sample_t *tab = demux_res->time_to_sample; - while (i < demux_res->num_time_to_samples) + /* The 'sound_sample_loc' we have is PCM-based and not directly usable. + * We need to convert it to an MP4 sample number 'sample_i' first. */ + sample_i = sound_sample_i = 0; + for (time = 0; time < demux_res->num_time_to_samples; ++time) { - tmp_cnt = tab[i].sample_count; - tmp_dur = tab[i].sample_duration; - tmp_var = tmp_cnt * tmp_dur; - if (sound_sample_loc <= new_sound_sample + tmp_var) + time_cnt = tts_tab[time].sample_count; + time_dur = tts_tab[time].sample_duration; + uint32_t time_var = time_cnt * time_dur; + + if (sound_sample_loc < sound_sample_i + time_var) { - tmp_var = (sound_sample_loc - new_sound_sample); - new_sample += tmp_var / tmp_dur; - new_sound_sample += tmp_var; + time_var = sound_sample_loc - sound_sample_i; + sample_i += time_var / time_dur; break; } - new_sample += tmp_cnt; - new_sound_sample += tmp_var; - ++i; + + sample_i += time_cnt; + sound_sample_i += time_var; + } + + /* Find the chunk after 'sample_i'. */ + for (chunk = 1; chunk < demux_res->num_lookup_table; ++chunk) + { + if (tco_tab[chunk].offset == 0) + break; + if (tco_tab[chunk].sample > sample_i) + break; } - /* We know the new sample (=frame), now calculate the file position. */ - gather_offset(demux_res, &new_sample, &new_pos); + /* The preceding chunk is the one that contains 'sample_i'. */ + chunk--; + chunk_first_sample = tco_tab[chunk].sample; + offset = tco_tab[chunk].offset; - /* We know the new file position, so let's try to seek to it */ - if (stream->ci->seek_buffer(new_pos)) + /* Compute the PCM sample number of the chunk's first sample + * to get an accurate base for sound_sample_i. */ + i = sound_sample_i = 0; + for (time = 0; time < demux_res->num_time_to_samples; ++time) { - *sound_samples_done = new_sound_sample; - *current_sample = new_sample; + time_cnt = tts_tab[time].sample_count; + time_dur = tts_tab[time].sample_duration; + + if (chunk_first_sample < i + time_cnt) + { + sound_sample_i += (chunk_first_sample - i) * time_dur; + break; + } + + i += time_cnt; + sound_sample_i += time_cnt * time_dur; + } + + DEBUGF("seek chunk=%lu, sample=%lu, soundsample=%lu, offset=%lu\n", + (unsigned long)chunk, (unsigned long)chunk_first_sample, + (unsigned long)sound_sample_i, (unsigned long)offset); + + if (tsz_tab) { + /* We have a sample-to-bytes table available so we can do accurate + * seeking. Move one sample at a time and update the file offset and + * PCM sample offset as we go. */ + for (i = chunk_first_sample; + i < sample_i && i < demux_res->num_sample_byte_sizes; ++i) + { + /* this could be unnecessary */ + if (time_cnt == 0 && ++time < demux_res->num_time_to_samples) + { + time_cnt = tts_tab[time].sample_count; + time_dur = tts_tab[time].sample_duration; + } + + offset += tsz_tab[i]; + sound_sample_i += time_dur; + time_cnt--; + } + } else { + /* No sample-to-bytes table available so we can only seek to the + * start of a chunk, which is often much lower resolution. */ + sample_i = chunk_first_sample; + } + + if (stream->ci->seek_buffer(offset)) + { + *sound_samples_done = sound_sample_i; + *current_sample = sample_i; return 1; } - + return 0; } |