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mp3enc: support MPEG-2 and MPEG-2.5 in Xing header.

This commit is contained in:
Clément Bœsch 2012-05-09 22:39:40 +02:00 committed by Anton Khirnov
parent 6365e4db79
commit ca8e39dd0d
1 changed files with 17 additions and 7 deletions
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24
libavformat/mp3enc.c
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@ -90,25 +90,34 @@ typedef struct MP3Context {
AVPacketList *queue, *queue_end;
} MP3Context;
static const uint8_t xing_offtbl[2][2] = {{32, 17}, {17, 9}};
/* insert a dummy frame containing number of frames */
static void mp3_write_xing(AVFormatContext *s)
{
MP3Context *mp3 = s->priv_data;
AVCodecContext *codec = s->streams[mp3->audio_stream_idx]->codec;
int bitrate_idx = 1; // 32 kbps
int64_t xing_offset = (codec->channels == 2) ? 32 : 17;
int32_t header;
MPADecodeHeader mpah;
int srate_idx, i, channels;
int xing_offset;
int ver = 0;
if (!s->pb->seekable)
return;
for (i = 0; i < FF_ARRAY_ELEMS(avpriv_mpa_freq_tab); i++)
if (avpriv_mpa_freq_tab[i] == codec->sample_rate) {
srate_idx = i;
break;
}
for (i = 0; i < FF_ARRAY_ELEMS(avpriv_mpa_freq_tab); i++) {
const uint16_t base_freq = avpriv_mpa_freq_tab[i];
if (codec->sample_rate == base_freq) ver = 0x3; // MPEG 1
else if (codec->sample_rate == base_freq / 2) ver = 0x2; // MPEG 2
else if (codec->sample_rate == base_freq / 4) ver = 0x0; // MPEG 2.5
else continue;
srate_idx = i;
break;
}
if (i == FF_ARRAY_ELEMS(avpriv_mpa_freq_tab)) {
av_log(s, AV_LOG_WARNING, "Unsupported sample rate, not writing Xing "
"header.\n");
@ -125,13 +134,14 @@ static void mp3_write_xing(AVFormatContext *s)
/* dummy MPEG audio header */
header = 0xff << 24; // sync
header |= (0x7 << 5 | 0x3 << 3 | 0x1 << 1 | 0x1) << 16; // sync/mpeg-1/layer 3/no crc*/
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 |= channels << 6;
avio_wb32(s->pb, header);
avpriv_mpegaudio_decode_header(&mpah, header);
xing_offset = xing_offtbl[ver != 3][codec->channels == 1];
ffio_fill(s->pb, 0, xing_offset);
ffio_wfourcc(s->pb, "Xing");
avio_wb32(s->pb, 0x1); // only number of frames