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demux_audo: fix wrong runtime and average bitrate for VBR MP3

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Do so by determining the number of frames from the Xing/Info/VBRI
headers and by calculation a correct duration which leads to an
reasonable average bytes per seconds.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@34273 b3059339-0415-0410-9bf9-f77b7e298cf2
Author: ib
This commit is contained in:
mplayer-svn 2011-10-27 20:09:09 +00:00 committed by wm4
parent 273d1ddd71
commit b8c3a20f5e
1 changed files with 67 additions and 1 deletions
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68
libmpdemux/demux_audio.c
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@ -257,6 +257,69 @@ get_flac_metadata (demuxer_t* demuxer)
}
#endif
/**
* @brief Determine the number of frames of a file encoded with
* variable bitrate mode (VBR).
*
* @param s stream to be read
* @param off offset in stream to start reading from
*
* @return 0 (error or no variable bitrate mode) or number of frames
*/
static unsigned int mp3_vbr_frames(stream_t *s, off_t off) {
static const int xing_offset[2][2] = {{32, 17}, {17, 9}};
unsigned int data;
unsigned char hdr[4];
int framesize, chans, spf, layer;
if ((s->flags & MP_STREAM_SEEK) == MP_STREAM_SEEK) {
if (!stream_seek(s, off)) return 0;
data = stream_read_dword(s);
hdr[0] = data >> 24;
hdr[1] = data >> 16;
hdr[2] = data >> 8;
hdr[3] = data;
if (!mp_check_mp3_header(data)) return 0;
framesize = mp_get_mp3_header(hdr, &chans, NULL, &spf, &layer, NULL);
if (framesize == -1 || layer != 3) return 0;
/* Xing / Info (at variable position: 32, 17 or 9 bytes after header) */
if (!stream_skip(s, xing_offset[spf < 1152][chans == 1])) return 0;
data = stream_read_dword(s);
if (data == MKBETAG('X','i','n','g') || data == MKBETAG('I','n','f','o')) {
data = stream_read_dword(s);
if (data & 0x1) // frames field is present
return stream_read_dword(s); // frames
}
/* VBRI (at fixed position: 32 bytes after header) */
if (!stream_seek(s, off + 4 + 32)) return 0;
data = stream_read_dword(s);
if (data == MKBETAG('V','B','R','I')) {
data = stream_read_word(s);
if (data == 1) { // check version
if (!stream_skip(s, 8)) return 0; // skip delay, quality and bytes
return stream_read_dword(s); // frames
}
}
}
return 0;
}
static int demux_audio_open(demuxer_t* demuxer) {
stream_t *s;
sh_audio_t* sh_audio;
@ -266,6 +329,7 @@ static int demux_audio_open(demuxer_t* demuxer) {
// mp3_hdrs list is sorted first by next_frame_pos and then by frame_pos
mp3_hdr_t *mp3_hdrs = NULL, *mp3_found = NULL;
da_priv_t* priv;
double duration;
s = demuxer->stream;
@ -342,7 +406,7 @@ static int demux_audio_open(demuxer_t* demuxer) {
sh_audio->wf->nBlockAlign = mp3_found->mpa_spf;
sh_audio->wf->wBitsPerSample = 16;
sh_audio->wf->cbSize = 0;
sh_audio->i_bps = sh_audio->wf->nAvgBytesPerSec;
duration = (double) mp3_vbr_frames(s, demuxer->movi_start) * mp3_found->mpa_spf / mp3_found->mp3_freq;
free(mp3_found);
mp3_found = NULL;
if(s->end_pos && (s->flags & MP_STREAM_SEEK) == MP_STREAM_SEEK) {
@ -378,6 +442,8 @@ static int demux_audio_open(demuxer_t* demuxer) {
demux_info_add(demuxer,"Genre",genres[g]);
}
}
if (duration && demuxer->movi_end && demuxer->movi_end > demuxer->movi_start) sh_audio->wf->nAvgBytesPerSec = (demuxer->movi_end - demuxer->movi_start) / duration;
sh_audio->i_bps = sh_audio->wf->nAvgBytesPerSec;
break;
case WAV: {
unsigned int chunk_type;