libavformat/aacdec.c
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 /*
  * raw ADTS AAC demuxer
  * Copyright (c) 2008 Michael Niedermayer <michaelni@gmx.at>
  * Copyright (c) 2009 Robert Swain ( rob opendot cl )
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include "libavutil/intreadwrite.h"
 #include "avformat.h"
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 #include "avio_internal.h"
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 #include "internal.h"
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 #include "id3v1.h"
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 #include "id3v2.h"
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 #include "apetag.h"
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 #define ADTS_HEADER_SIZE 7
 
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 static int adts_aac_probe(AVProbeData *p)
 {
     int max_frames = 0, first_frames = 0;
     int fsize, frames;
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     const uint8_t *buf0 = p->buf;
     const uint8_t *buf2;
     const uint8_t *buf;
     const uint8_t *end = buf0 + p->buf_size - 7;
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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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             uint32_t header = AV_RB16(buf2);
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             if ((header & 0xFFF6) != 0xFFF0) {
                 if (buf != buf0) {
                     // Found something that isn't an ADTS header, starting
                     // from a position other than the start of the buffer.
                     // Discard the count we've accumulated so far since it
                     // probably was a false positive.
                     frames = 0;
                 }
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                 break;
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             }
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             fsize = (AV_RB32(buf2 + 3) >> 13) & 0x1FFF;
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             if (fsize < 7)
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                 break;
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             fsize = FFMIN(fsize, end - buf2);
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             buf2 += fsize;
         }
         max_frames = FFMAX(max_frames, frames);
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         if (buf == buf0)
             first_frames = frames;
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     }
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     if (first_frames >= 3)
         return AVPROBE_SCORE_EXTENSION + 1;
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     else if (max_frames > 100)
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         return AVPROBE_SCORE_EXTENSION;
     else if (max_frames >= 3)
         return AVPROBE_SCORE_EXTENSION / 2;
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     else if (first_frames >= 1)
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         return 1;
     else
         return 0;
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 }
 
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 static int adts_aac_read_header(AVFormatContext *s)
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 {
     AVStream *st;
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     uint16_t state;
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     st = avformat_new_stream(s, NULL);
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     if (!st)
         return AVERROR(ENOMEM);
 
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     st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
     st->codecpar->codec_id   = s->iformat->raw_codec_id;
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     st->need_parsing         = AVSTREAM_PARSE_FULL_RAW;
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     ff_id3v1_read(s);
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     if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
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         !av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
         int64_t cur = avio_tell(s->pb);
         ff_ape_parse_tag(s);
         avio_seek(s->pb, cur, SEEK_SET);
     }
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     // skip data until the first ADTS frame is found
     state = avio_r8(s->pb);
     while (!avio_feof(s->pb) && avio_tell(s->pb) < s->probesize) {
         state = (state << 8) | avio_r8(s->pb);
         if ((state >> 4) != 0xFFF)
             continue;
         avio_seek(s->pb, -2, SEEK_CUR);
         break;
     }
     if ((state >> 4) != 0xFFF)
         return AVERROR_INVALIDDATA;
 
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     // LCM of all possible ADTS sample rates
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     avpriv_set_pts_info(st, 64, 1, 28224000);
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     return 0;
 }
 
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 static int handle_id3(AVFormatContext *s, AVPacket *pkt)
 {
     AVDictionary *metadata = NULL;
     AVIOContext ioctx;
     ID3v2ExtraMeta *id3v2_extra_meta = NULL;
     int ret;
 
     ret = av_append_packet(s->pb, pkt, ff_id3v2_tag_len(pkt->data) - pkt->size);
     if (ret < 0) {
         av_packet_unref(pkt);
         return ret;
     }
 
     ffio_init_context(&ioctx, pkt->data, pkt->size, 0, NULL, NULL, NULL, NULL);
     ff_id3v2_read_dict(&ioctx, &metadata, ID3v2_DEFAULT_MAGIC, &id3v2_extra_meta);
     if ((ret = ff_id3v2_parse_priv_dict(&metadata, &id3v2_extra_meta)) < 0)
         goto error;
 
     if (metadata) {
         if ((ret = av_dict_copy(&s->metadata, metadata, 0)) < 0)
             goto error;
         s->event_flags |= AVFMT_EVENT_FLAG_METADATA_UPDATED;
     }
 
 error:
     av_packet_unref(pkt);
     ff_id3v2_free_extra_meta(&id3v2_extra_meta);
     av_dict_free(&metadata);
 
     return ret;
 }
 
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 static int adts_aac_read_packet(AVFormatContext *s, AVPacket *pkt)
 {
     int ret, fsize;
 
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     // Parse all the ID3 headers between frames
     while (1) {
         ret = av_get_packet(s->pb, pkt, FFMAX(ID3v2_HEADER_SIZE, ADTS_HEADER_SIZE));
         if (ret >= ID3v2_HEADER_SIZE && ff_id3v2_match(pkt->data, ID3v2_DEFAULT_MAGIC)) {
             if ((ret = handle_id3(s, pkt)) >= 0) {
                 continue;
             }
         }
         break;
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     }
 
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     if (ret < 0)
         return ret;
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     if (ret < ADTS_HEADER_SIZE) {
         av_packet_unref(pkt);
         return AVERROR(EIO);
     }
 
     if ((AV_RB16(pkt->data) >> 4) != 0xfff) {
         av_packet_unref(pkt);
         return AVERROR_INVALIDDATA;
     }
 
     fsize = (AV_RB32(pkt->data + 3) >> 13) & 0x1FFF;
     if (fsize < ADTS_HEADER_SIZE) {
         av_packet_unref(pkt);
         return AVERROR_INVALIDDATA;
     }
 
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     ret = av_append_packet(s->pb, pkt, fsize - pkt->size);
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     if (ret < 0)
         av_packet_unref(pkt);
 
     return ret;
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 }
 
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 AVInputFormat ff_aac_demuxer = {
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     .name         = "aac",
     .long_name    = NULL_IF_CONFIG_SMALL("raw ADTS AAC (Advanced Audio Coding)"),
     .read_probe   = adts_aac_probe,
     .read_header  = adts_aac_read_header,
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     .read_packet  = adts_aac_read_packet,
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     .flags        = AVFMT_GENERIC_INDEX,
     .extensions   = "aac",
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     .mime_type    = "audio/aac,audio/aacp,audio/x-aac",
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     .raw_codec_id = AV_CODEC_ID_AAC,
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 };