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mp3enc: Properly write bitrate value in XING header 

Instead of using a fixed bitrate_idx, calculate a matching bitrate for
the XING header.

Using a fixed bitrate_idx causes tools such as file(1) and mediainfo(1)
to report wrong bitrate and bitrate mode when using CBR.

Bug-Id: https://bugs.debian.org/736088

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
This commit is contained in:
Michael Niedermayer 2014-04-09 18:22:53 +02:00 committed by Luca Barbato
parent 254c95cdd1
commit 617a1a98a6
1 changed files with 39 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
libavformat/mp3enc.c
View File

@ -119,8 +119,11 @@ static void mp3_write_xing(AVFormatContext *s)
MPADecodeHeader mpah;
int srate_idx, i, channels;
int bitrate_idx;
int best_bitrate_idx;
int best_bitrate_error = INT_MAX;
int xing_offset;
int ver = 0;
int lsf, bytes_needed;
if (!s->pb->seekable || !mp3->write_xing)
return;
@ -150,21 +153,51 @@ static void mp3_write_xing(AVFormatContext *s)
return;
}
/* 64 kbps frame, should be large enough */
bitrate_idx = (ver == 3) ? 5 : 8;
/* dummy MPEG audio header */
header = 0xff << 24; // sync
header |= (0x7 << 5 | ver << 3 | 0x1 << 1 | 0x1) << 16; // sync/audio-version/layer 3/no crc*/
header |= (bitrate_idx << 4 | srate_idx << 2) << 8;
header |= (srate_idx << 2) << 8;
header |= channels << 6;
lsf = !((header & (1 << 20) && header & (1 << 19)));
xing_offset = xing_offtbl[ver != 3][channels == 1];
bytes_needed = 4 // header
+ xing_offset
+ 4 // xing tag
+ 4 // frames/size/toc flags
+ 4 // frames
+ 4 // size
+ XING_TOC_SIZE; // toc
for (bitrate_idx = 1; bitrate_idx < 15; bitrate_idx++) {
int bit_rate = 1000 * avpriv_mpa_bitrate_tab[lsf][3 - 1][bitrate_idx];
int error = FFABS(bit_rate - codec->bit_rate);
if (error < best_bitrate_error){
best_bitrate_error = error;
best_bitrate_idx = bitrate_idx;
}
}
for (bitrate_idx = best_bitrate_idx; bitrate_idx < 15; bitrate_idx++) {
int32_t mask = bitrate_idx << (4 + 8);
header |= mask;
avpriv_mpegaudio_decode_header(&mpah, header);
if (bytes_needed <= mpah.frame_size)
break;
header &= ~mask;
}
avio_wb32(s->pb, header);
avpriv_mpegaudio_decode_header(&mpah, header);
av_assert0(mpah.frame_size >= XING_MAX_SIZE);
xing_offset = xing_offtbl[ver != 3][codec->channels == 1];
ffio_fill(s->pb, 0, xing_offset);
mp3->xing_offset = avio_tell(s->pb);
ffio_wfourcc(s->pb, "Xing");
@ -180,8 +213,7 @@ static void mp3_write_xing(AVFormatContext *s)
for (i = 0; i < XING_TOC_SIZE; i++)
avio_w8(s->pb, 255 * i / XING_TOC_SIZE);
mpah.frame_size -= 4 + xing_offset + 4 + 4 + 4 + 4 + XING_TOC_SIZE;
ffio_fill(s->pb, 0, mpah.frame_size);
ffio_fill(s->pb, 0, mpah.frame_size - bytes_needed);
}
/*