diff options
| -rw-r--r-- | src/demuxers/demux_mpeg_block.c | 58 |
1 files changed, 39 insertions, 19 deletions
diff --git a/src/demuxers/demux_mpeg_block.c b/src/demuxers/demux_mpeg_block.c index 8d6c0279d..8a08524d8 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 1.147 2002/12/08 21:43:51 miguelfreitas Exp $ + * $Id: demux_mpeg_block.c,v 1.148 2002/12/15 01:05:36 rockyb Exp $ * * demultiplexer for mpeg 1/2 program streams * @@ -640,35 +640,55 @@ static int demux_mpeg_block_send_chunk (demux_plugin_t *this_gen) { return this->status; } -/* estimate bitrate */ +/*! + Estimate bitrate by looking inside the MPEG file for presentation + time stamps (PTS) and computing how far apart these are + in bytes and in time. + + On failure return 0. +*/ + +/* How many *sucessful* PTS samples do we take? */ +#define MAX_SAMPLES 5 + +/* How many times we read blocks before giving up. */ +#define MAX_READS 30 + +/* TRUNCATE x to the nearest multiple of y. */ +#define TRUNC(x,y) (((x) / (y)) * (y)) static int demux_mpeg_block_estimate_rate (demux_mpeg_block_t *this) { buf_element_t *buf = NULL; unsigned char *p; int is_mpeg1=0; - off_t pos, last_pos; - off_t step; - int64_t pts, last_pts; - int rate; - int count; + off_t pos, last_pos=0; + off_t step, mpeg_length; + off_t blocksize = this->blocksize; + int64_t pts, last_pts=0; + int reads=0 /* Number of blocks read so far */; + int count=0; /* Number of sucessful PTS found so far */ + int rate=0; /* The return rate value */ int stream_id; + /* We can't estimate by sampling if we don't thave the ability to + randomly access the and more importantly reset after accessessing. */ if (!(this->input->get_capabilities(this->input) & INPUT_CAP_SEEKABLE)) return 0; - last_pos = 0; - last_pts = 0; - rate = 0; - step = this->input->get_length (this->input) / 10; - step = (step / this->blocksize) * this->blocksize; - if (step <= 0) step = this->blocksize; /* avoid endless loop for tiny files */ - pos = step; - count = 0; + mpeg_length= this->input->get_length (this->input); + step = TRUNC((mpeg_length/MAX_SAMPLES), blocksize); + if (step <= 0) step = blocksize; /* avoid endless loop for tiny files */ + pos = step; + + /* At this point "pos", and "step" are a multiple of blocksize and + they should continue to be so throughout. + */ this->input->seek (this->input, pos, SEEK_SET); - while ((buf = this->input->read_block (this->input, this->video_fifo, this->blocksize)) ) { + while ( (buf = this->input->read_block (this->input, this->video_fifo, blocksize)) + && count < MAX_SAMPLES && reads++ < MAX_READS ) { p = buf->content; /* len = this->mnBlocksize; */ @@ -698,7 +718,7 @@ static int demux_mpeg_block_estimate_rate (demux_mpeg_block_t *this) { pts = 0; if ((stream_id < 0xbc) || ((stream_id & 0xf0) != 0xe0)) { - pos += (off_t) this->blocksize; + pos += (off_t) blocksize; buf->free_buffer (buf); continue; /* only use video packets */ } @@ -762,11 +782,11 @@ static int demux_mpeg_block_estimate_rate (demux_mpeg_block_t *this) { last_pts = pts; pos += step; } else - pos += (off_t) this->blocksize; + pos += blocksize; buf->free_buffer (buf); - if (this->input->seek (this->input, pos, SEEK_SET) == (off_t)-1) + if (pos > mpeg_length || this->input->seek (this->input, pos, SEEK_SET) == (off_t)-1) break; } |