diff options
| -rw-r--r-- | src/demuxers/demux_mpeg_block.c | 96 |
1 files changed, 93 insertions, 3 deletions
diff --git a/src/demuxers/demux_mpeg_block.c b/src/demuxers/demux_mpeg_block.c index b9428bf72..dd8342312 100644 --- a/src/demuxers/demux_mpeg_block.c +++ b/src/demuxers/demux_mpeg_block.c @@ -17,7 +17,7 @@ * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA * - * $Id: demux_mpeg_block.c,v 1.199 2003/11/16 15:31:51 mroi Exp $ + * $Id: demux_mpeg_block.c,v 1.200 2003/11/16 22:20:08 jcdutton Exp $ * * demultiplexer for mpeg 1/2 program streams * used with fixed blocksize devices (like dvd/vcd) @@ -769,8 +769,98 @@ static int32_t parse_private_stream_1(demux_mpeg_block_t *this, uint8_t *p, buf_ if ((p[0]&0xF0) == 0x80) { track = p[0] & 0x0F; /* hack : ac3 track */ - buf->decoder_info[1] = p[1]; /* Number of frame headers */ - buf->decoder_info[2] = p[2] << 8 | p[3]; /* First access unit pointer */ + + /* Number of frame headers + * + * Describes the number of a52 frame headers that start in this pack (One pack per DVD sector). + * + * Likely values: 1 or 2. + */ + buf->decoder_info[1] = p[1]; + /* First access unit pointer. + * + * Describes the byte offset within this pack to the beginning of the first A52 frame header. + * The PTS from this pack applies to the beginning of the first A52 frame that starts in this pack. + * Any bytes before this offset should be considered to belong to the previous A52 frame. + * and therefore be tagged with a PTS value derived from the previous pack. + * + * Likely values: Anything from 1 to the size of an A52 frame. + */ + buf->decoder_info[2] = p[2] << 8 | p[3]; + /* Summary: If the first pack contains the beginning of 2 A52 frames( decoder_info[1]=2), + * the PTS value applies to the first A52 frame. + * The second A52 frame will have no PTS value. + * The start of the next pack will contain the rest of the second A52 frame and thus, no PTS value. + * The third A52 frame will have the PTS value from the second pack. + * + * If the first pack contains the beginning of 1 frame( decoder_info[1]=1 ), + * this first pack must then contain a certain amount of the previous A52 frame. + * the PTS value will not apply to this previous A52 frame, + * the PTS value will apply to the beginning of the frame that begins in this pack. + * + * LPCM note: The first_access_unit_pointer will point to + * the PCM sample within the pack at which the PTS values applies. + * + * Example to values in a real stream, each line is a pack (dvd sector): - + * decoder_info[1], decoder_info[2], PTS + * 2 5 125640 + * 1 1061 131400 + * 1 581 134280 + * 2 101 137160 + * 1 1157 142920 + * 1 677 145800 + * 2 197 148680 + * 1 1253 154440 + * 1 773 157320 + * 2 293 160200 + * 1 1349 165960 + * 1 869 168840 + * 2 389 171720 + * 1 1445 177480 + * 1 965 180360 + * 1 485 183240 + * 2 5 186120 + * 1 1061 191880 + * 1 581 194760 + * 2 101 197640 + * 1 1157 203400 + * 1 677 206280 + * 2 197 209160 + * Notice the repeating pattern of both decoder_info[1] and decoder_info[2]. + * The resulting A52 frames will have these PTS values: - + * PTS + * 125640 + * 0 + * 131400 + * 134280 + * 137160 + * 0 + * 142920 + * 145800 + * 148680 + * 0 + * 154440 + * 157320 + * 160200 + * 0 + * 165960 + * 168840 + * 171720 + * 0 + * 177480 + * 180360 + * 183240 + * 186120 + * 0 + * 191880 + * 194760 + * 197640 + * 0 + * 203400 + * 206280 + * 209160 + * 0 (Partial A52 frame.) + */ buf->content = p+4; buf->size = this->packet_len-4; |