MrBesen/ffmpeg
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

mp3dec: move XING/Info and VBRI parsing into their own functions

Browse Source 
Signed-off-by: Anton Khirnov <anton@khirnov.net>
This commit is contained in:
Alessandro Ghedini 2014-04-12 18:25:41 +02:00 committed by Anton Khirnov
parent ae43c10e36
commit fbd8e04210
1 changed files with 58 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

93
libavformat/mp3dec.c
View File

@ -39,6 +39,9 @@
typedef struct MP3DecContext {
int xing_toc;
unsigned frames; /* Total number of frames in file */
unsigned size; /* Total number of bytes in the stream */
int is_cbr;
} MP3DecContext;
/* mp3 read */
@ -125,18 +128,60 @@ static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration
mp3->xing_toc = 1;
}
static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st,
MPADecodeHeader *c, uint32_t spf)
{
uint32_t v;
MP3DecContext *mp3 = s->priv_data;
const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
/* Check for Xing / Info tag */
avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]);
v = avio_rb32(s->pb);
mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
if (v == MKBETAG('X', 'i', 'n', 'g') || mp3->is_cbr) {
v = avio_rb32(s->pb);
if (v & XING_FLAG_FRAMES)
mp3->frames = avio_rb32(s->pb);
if (v & XING_FLAG_SIZE)
mp3->size = avio_rb32(s->pb);
if (v & XING_FLAG_TOC && mp3->frames)
read_xing_toc(s, mp3->size,
av_rescale_q(mp3->frames,
(AVRational){spf, c->sample_rate},
st->time_base));
}
}
static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base)
{
uint32_t v;
MP3DecContext *mp3 = s->priv_data;
/* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
avio_seek(s->pb, base + 4 + 32, SEEK_SET);
v = avio_rb32(s->pb);
if (v == MKBETAG('V', 'B', 'R', 'I')) {
/* Check tag version */
if (avio_rb16(s->pb) == 1) {
/* skip delay and quality */
avio_skip(s->pb, 4);
mp3->size = avio_rb32(s->pb);
mp3->frames = avio_rb32(s->pb);
}
}
}
/**
* Try to find Xing/Info/VBRI tags and compute duration from info therein
*/
static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
{
uint32_t v, spf;
unsigned frames = 0; /* Total number of frames in file */
unsigned size = 0; /* Total number of bytes in the stream */
const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
MPADecodeHeader c;
int vbrtag_size = 0;
int is_cbr;
MP3DecContext *mp3 = s->priv_data;
v = avio_rb32(s->pb);
if(ff_mpa_check_header(v) < 0)
@ -149,45 +194,23 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
/* Check for Xing / Info tag */
avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
v = avio_rb32(s->pb);
is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
if (v == MKBETAG('X', 'i', 'n', 'g') || is_cbr) {
v = avio_rb32(s->pb);
if(v & XING_FLAG_FRAMES)
frames = avio_rb32(s->pb);
if(v & XING_FLAG_SIZE)
size = avio_rb32(s->pb);
if (v & XING_FLAG_TOC && frames)
read_xing_toc(s, size, av_rescale_q(frames, (AVRational){spf, c.sample_rate},
st->time_base));
}
mp3->frames = 0;
mp3->size = 0;
/* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
avio_seek(s->pb, base + 4 + 32, SEEK_SET);
v = avio_rb32(s->pb);
if(v == MKBETAG('V', 'B', 'R', 'I')) {
/* Check tag version */
if(avio_rb16(s->pb) == 1) {
/* skip delay and quality */
avio_skip(s->pb, 4);
size = avio_rb32(s->pb);
frames = avio_rb32(s->pb);
}
}
mp3_parse_info_tag(s, st, &c, spf);
mp3_parse_vbri_tag(s, st, base);
if(!frames && !size)
if (!mp3->frames && !mp3->size)
return -1;
/* Skip the vbr tag frame */
avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
if(frames)
st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
if (mp3->frames)
st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate},
st->time_base);
if (size && frames && !is_cbr)
st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
if (mp3->size && mp3->frames && !mp3->is_cbr)
st->codec->bit_rate = av_rescale(mp3->size, 8 * c.sample_rate, mp3->frames * (int64_t)spf);
return 0;
}