mirror of
https://github.com/FFmpeg/FFmpeg.git
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274 lines
7.9 KiB
C
274 lines
7.9 KiB
C
/*
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* MP3 demuxer
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* Copyright (c) 2003 Fabrice Bellard
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "libavutil/avstring.h"
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#include "libavutil/intreadwrite.h"
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#include "libavutil/dict.h"
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#include "libavutil/mathematics.h"
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#include "avformat.h"
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#include "internal.h"
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#include "id3v2.h"
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#include "id3v1.h"
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#include "libavcodec/mpegaudiodecheader.h"
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#define XING_FLAG_FRAMES 0x01
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#define XING_FLAG_SIZE 0x02
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#define XING_FLAG_TOC 0x04
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#define XING_TOC_COUNT 100
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/* mp3 read */
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static int mp3_read_probe(AVProbeData *p)
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{
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int max_frames, first_frames = 0;
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int fsize, frames, sample_rate;
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uint32_t header;
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uint8_t *buf, *buf0, *buf2, *end;
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AVCodecContext avctx;
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buf0 = p->buf;
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end = p->buf + p->buf_size - sizeof(uint32_t);
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while(buf0 < end && !*buf0)
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buf0++;
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max_frames = 0;
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buf = buf0;
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for(; buf < end; buf= buf2+1) {
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buf2 = buf;
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for(frames = 0; buf2 < end; frames++) {
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header = AV_RB32(buf2);
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fsize = avpriv_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
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if(fsize < 0)
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break;
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buf2 += fsize;
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}
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max_frames = FFMAX(max_frames, frames);
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if(buf == buf0)
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first_frames= frames;
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}
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// keep this in sync with ac3 probe, both need to avoid
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// issues with MPEG-files!
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if (first_frames >= 4) return AVPROBE_SCORE_MAX / 2 + 1;
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if (max_frames) {
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int pes = 0, i;
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unsigned int code = -1;
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#define VIDEO_ID 0x000001e0
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#define AUDIO_ID 0x000001c0
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/* do a search for mpegps headers to be able to properly bias
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* towards mpegps if we detect this stream as both. */
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for (i = 0; i<p->buf_size; i++) {
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code = (code << 8) + p->buf[i];
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if ((code & 0xffffff00) == 0x100) {
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if ((code & 0x1f0) == VIDEO_ID) pes++;
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else if((code & 0x1e0) == AUDIO_ID) pes++;
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}
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}
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if (pes)
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max_frames = (max_frames + pes - 1) / pes;
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}
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if (max_frames > 500) return AVPROBE_SCORE_MAX / 2;
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else if (max_frames >= 4) return AVPROBE_SCORE_MAX / 4;
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else if (max_frames >= 1) return 1;
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else return 0;
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//mpegps_mp3_unrecognized_format.mpg has max_frames=3
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}
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static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
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{
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int i;
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if (!filesize &&
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!(filesize = avio_size(s->pb))) {
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av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
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return;
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}
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for (i = 0; i < XING_TOC_COUNT; i++) {
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uint8_t b = avio_r8(s->pb);
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av_add_index_entry(s->streams[0],
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av_rescale(b, filesize, 256),
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av_rescale(i, duration, XING_TOC_COUNT),
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0, 0, AVINDEX_KEYFRAME);
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}
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}
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/**
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* Try to find Xing/Info/VBRI tags and compute duration from info therein
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*/
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static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
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{
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uint32_t v, spf;
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unsigned frames = 0; /* Total number of frames in file */
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unsigned size = 0; /* Total number of bytes in the stream */
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const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
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MPADecodeHeader c;
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int vbrtag_size = 0;
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v = avio_rb32(s->pb);
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if(ff_mpa_check_header(v) < 0)
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return -1;
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if (avpriv_mpegaudio_decode_header(&c, v) == 0)
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vbrtag_size = c.frame_size;
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if(c.layer != 3)
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return -1;
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spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
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/* Check for Xing / Info tag */
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avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
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v = avio_rb32(s->pb);
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if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) {
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v = avio_rb32(s->pb);
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if(v & XING_FLAG_FRAMES)
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frames = avio_rb32(s->pb);
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if(v & XING_FLAG_SIZE)
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size = avio_rb32(s->pb);
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if (v & XING_FLAG_TOC && frames)
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read_xing_toc(s, size, av_rescale_q(frames, (AVRational){spf, c.sample_rate},
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st->time_base));
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}
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/* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
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avio_seek(s->pb, base + 4 + 32, SEEK_SET);
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v = avio_rb32(s->pb);
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if(v == MKBETAG('V', 'B', 'R', 'I')) {
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/* Check tag version */
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if(avio_rb16(s->pb) == 1) {
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/* skip delay and quality */
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avio_skip(s->pb, 4);
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size = avio_rb32(s->pb);
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frames = avio_rb32(s->pb);
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}
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}
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if(!frames && !size)
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return -1;
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/* Skip the vbr tag frame */
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avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
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if(frames)
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st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
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st->time_base);
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if(size && frames)
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st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
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return 0;
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}
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static int mp3_read_header(AVFormatContext *s)
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{
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AVStream *st;
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int64_t off;
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st = avformat_new_stream(s, NULL);
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if (!st)
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return AVERROR(ENOMEM);
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st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
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st->codec->codec_id = AV_CODEC_ID_MP3;
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st->need_parsing = AVSTREAM_PARSE_FULL;
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st->start_time = 0;
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// lcm of all mp3 sample rates
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avpriv_set_pts_info(st, 64, 1, 14112000);
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off = avio_tell(s->pb);
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if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
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ff_id3v1_read(s);
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if (mp3_parse_vbr_tags(s, st, off) < 0)
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avio_seek(s->pb, off, SEEK_SET);
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/* the parameters will be extracted from the compressed bitstream */
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return 0;
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}
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#define MP3_PACKET_SIZE 1024
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static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
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{
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int ret;
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ret = av_get_packet(s->pb, pkt, MP3_PACKET_SIZE);
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if (ret < 0)
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return ret;
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pkt->stream_index = 0;
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if (ret > ID3v1_TAG_SIZE &&
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memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
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ret -= ID3v1_TAG_SIZE;
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/* note: we need to modify the packet size here to handle the last
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packet */
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pkt->size = ret;
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return ret;
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}
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static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
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int flags)
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{
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AVIndexEntry *ie;
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AVStream *st = s->streams[0];
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int64_t ret = av_index_search_timestamp(st, timestamp, flags);
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uint32_t header = 0;
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if (ret < 0)
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return ret;
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ie = &st->index_entries[ret];
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ret = avio_seek(s->pb, ie->pos, SEEK_SET);
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if (ret < 0)
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return ret;
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while (!s->pb->eof_reached) {
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header = (header << 8) + avio_r8(s->pb);
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if (ff_mpa_check_header(header) >= 0) {
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ff_update_cur_dts(s, st, ie->timestamp);
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ret = avio_seek(s->pb, -4, SEEK_CUR);
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return (ret >= 0) ? 0 : ret;
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}
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}
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return AVERROR_EOF;
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}
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AVInputFormat ff_mp3_demuxer = {
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.name = "mp3",
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.long_name = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
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.read_probe = mp3_read_probe,
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.read_header = mp3_read_header,
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.read_packet = mp3_read_packet,
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.read_seek = mp3_seek,
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.flags = AVFMT_GENERIC_INDEX,
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.extensions = "mp2,mp3,m2a", /* XXX: use probe */
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};
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