diff options
| -rw-r--r-- | src/demuxers/demux_ac3.c | 150 |
1 files changed, 120 insertions, 30 deletions
diff --git a/src/demuxers/demux_ac3.c b/src/demuxers/demux_ac3.c index 285f0c8de..fad893623 100644 --- a/src/demuxers/demux_ac3.c +++ b/src/demuxers/demux_ac3.c @@ -21,7 +21,7 @@ * This demuxer detects raw AC3 data in a file and shovels AC3 data * directly to the AC3 decoder. * - * $Id: demux_ac3.c,v 1.2 2003/01/23 15:10:55 tmmm Exp $ + * $Id: demux_ac3.c,v 1.3 2003/01/29 03:36:04 tmmm Exp $ * */ @@ -42,6 +42,8 @@ #include "buffer.h" #include "bswap.h" +#define AC3_PREAMBLE_BYTES 5 + typedef struct { demux_plugin_t demux_plugin; @@ -56,6 +58,11 @@ typedef struct { input_plugin_t *input; int status; + int seek_flag; + + int sample_rate; /* 0 = 48KHz, 1 = 44.1KHz, 2 = 32KHz */ + int frame_size; + int running_time; char last_mrl[1024]; } demux_ac3_t; @@ -70,21 +77,91 @@ typedef struct { config_values_t *config; } demux_ac3_class_t; +/* borrow some knowledge from the AC3 decoder */ +struct frmsize_s +{ + uint16_t bit_rate; + uint16_t frm_size[3]; +}; + +static const struct frmsize_s frmsizecod_tbl[64] = +{ + { 32 ,{64 ,69 ,96 } }, + { 32 ,{64 ,70 ,96 } }, + { 40 ,{80 ,87 ,120 } }, + { 40 ,{80 ,88 ,120 } }, + { 48 ,{96 ,104 ,144 } }, + { 48 ,{96 ,105 ,144 } }, + { 56 ,{112 ,121 ,168 } }, + { 56 ,{112 ,122 ,168 } }, + { 64 ,{128 ,139 ,192 } }, + { 64 ,{128 ,140 ,192 } }, + { 80 ,{160 ,174 ,240 } }, + { 80 ,{160 ,175 ,240 } }, + { 96 ,{192 ,208 ,288 } }, + { 96 ,{192 ,209 ,288 } }, + { 112 ,{224 ,243 ,336 } }, + { 112 ,{224 ,244 ,336 } }, + { 128 ,{256 ,278 ,384 } }, + { 128 ,{256 ,279 ,384 } }, + { 160 ,{320 ,348 ,480 } }, + { 160 ,{320 ,349 ,480 } }, + { 192 ,{384 ,417 ,576 } }, + { 192 ,{384 ,418 ,576 } }, + { 224 ,{448 ,487 ,672 } }, + { 224 ,{448 ,488 ,672 } }, + { 256 ,{512 ,557 ,768 } }, + { 256 ,{512 ,558 ,768 } }, + { 320 ,{640 ,696 ,960 } }, + { 320 ,{640 ,697 ,960 } }, + { 384 ,{768 ,835 ,1152 } }, + { 384 ,{768 ,836 ,1152 } }, + { 448 ,{896 ,975 ,1344 } }, + { 448 ,{896 ,976 ,1344 } }, + { 512 ,{1024 ,1114 ,1536 } }, + { 512 ,{1024 ,1115 ,1536 } }, + { 576 ,{1152 ,1253 ,1728 } }, + { 576 ,{1152 ,1254 ,1728 } }, + { 640 ,{1280 ,1393 ,1920 } }, + { 640 ,{1280 ,1394 ,1920 } } +}; + /* returns 1 if the AC3 file was opened successfully, 0 otherwise */ static int open_ac3_file(demux_ac3_t *this) { - unsigned char sync_mark[2]; + unsigned char preamble[AC3_PREAMBLE_BYTES]; /* check if the sync mark matches up */ this->input->seek(this->input, 0, SEEK_SET); - if (this->input->read(this->input, sync_mark, 2) != 2) + if (this->input->read(this->input, preamble, AC3_PREAMBLE_BYTES) != + AC3_PREAMBLE_BYTES) return 0; - if ((sync_mark[0] == 0x0B) && - (sync_mark[1] == 0x77)) - return 1; - else + if ((preamble[0] != 0x0B) || + (preamble[1] != 0x77)) + return 0; + + this->sample_rate = preamble[4] >> 6; + if (this->sample_rate > 2) return 0; + + this->frame_size = + frmsizecod_tbl[preamble[4] & 0x3F].frm_size[this->sample_rate]; + + /* convert the sample rate to a more useful number */ + if (this->sample_rate == 0) + this->sample_rate = 48000; + else if (this->sample_rate == 1) + this->sample_rate = 44100; + else + this->sample_rate = 32000; + + this->running_time = this->input->get_length(this->input); + this->running_time /= this->frame_size; + this->running_time *= (90000 / 1000) * (256 * 3); + this->running_time /= this->sample_rate; + + return 1; } static int demux_ac3_send_chunk (demux_plugin_t *this_gen) { @@ -94,26 +171,41 @@ static int demux_ac3_send_chunk (demux_plugin_t *this_gen) { off_t current_file_pos; int64_t audio_pts; int bytes_read; + int frame_number; current_file_pos = this->input->get_current_pos(this->input); + frame_number = current_file_pos / this->frame_size; + + /* + * Each frame represents 256 new audio samples according to the a52 spec. + * Thus, the pts computation should work something like: + * + * pts = frame # * 256 samples 1 sec 90000 pts + * ----------- * ----------- * --------- + * 1 frame sample rate 1 sec + * + * For some reason, the computation only works out correctly + * assuming 256 * 3 = 768 samples/frame. + */ + audio_pts = frame_number; + audio_pts *= 90000; + audio_pts *= 256 * 3; + audio_pts /= this->sample_rate; + + if (this->seek_flag) { + xine_demux_control_newpts(this->stream, audio_pts, 0); + this->seek_flag = 0; + } - /* let the decoder sort out the pts for now */ - audio_pts = 0; - - /* read a buffer-sized block from the stream; if there is less than a - * buffer of data, send whatever there is; if there are no bytes returned, - * demux is finished */ buf = this->audio_fifo->buffer_pool_alloc (this->audio_fifo); buf->type = BUF_AUDIO_A52; - bytes_read = this->input->read(this->input, buf->content, buf->max_size); + bytes_read = this->input->read(this->input, buf->content, this->frame_size); if (bytes_read == 0) { buf->free_buffer(buf); this->status = DEMUX_FINISHED; return this->status; - } else if (bytes_read < buf->max_size) - buf->size = bytes_read; - else - buf->size = buf->max_size; + } + buf->size = bytes_read; buf->extra_info->input_pos = current_file_pos; buf->extra_info->input_length = this->input->get_length(this->input); @@ -158,17 +250,15 @@ static int demux_ac3_seek (demux_plugin_t *this_gen, demux_ac3_t *this = (demux_ac3_t *) this_gen; - /* if thread is not running, initialize demuxer */ - if( !this->stream->demux_thread_running ) { + /* divide the requested offset integer-wise by the frame alignment and + * multiply by the frame alignment to determine the new starting block */ + start_pos /= this->frame_size; + start_pos *= this->frame_size; + this->input->seek(this->input, start_pos, SEEK_SET); - /* send new pts */ - xine_demux_control_newpts(this->stream, 0, 0); - - this->status = DEMUX_OK; - - /* start at the beginning of the file */ - this->input->seek(this->input, 0, SEEK_SET); - } + this->seek_flag = 1; + this->status = DEMUX_OK; + xine_demux_flush_engine (this->stream); return this->status; } @@ -185,12 +275,12 @@ static int demux_ac3_get_status (demux_plugin_t *this_gen) { return this->status; } -/* return the approximate length in miliseconds */ +/* return the approximate length in milliseconds */ static int demux_ac3_get_stream_length (demux_plugin_t *this_gen) { demux_ac3_t *this = (demux_ac3_t *) this_gen; - return 0; + return this->running_time; } static uint32_t demux_ac3_get_capabilities(demux_plugin_t *this_gen) { |