xref: /third_party/ffmpeg/libavformat/aacdec.c (revision cabdff1a)

/*
 * 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/avassert.h"
#include "libavutil/intreadwrite.h"
#include "avformat.h"
#include "avio_internal.h"
#include "internal.h"
#include "id3v1.h"
#include "id3v2.h"
#include "apetag.h"

#define ADTS_HEADER_SIZE 7

static int adts_aac_probe(const AVProbeData *p)
{
    int max_frames = 0, first_frames = 0;
    int fsize, frames;
    const uint8_t *buf0 = p->buf;
    const uint8_t *buf2;
    const uint8_t *buf;
    const uint8_t *end = buf0 + p->buf_size - 7;

    buf = buf0;

    for (; buf < end; buf = buf2 + 1) {
        buf2 = buf;

        for (frames = 0; buf2 < end; frames++) {
            uint32_t header = AV_RB16(buf2);
            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;
                }
                break;
            }
            fsize = (AV_RB32(buf2 + 3) >> 13) & 0x1FFF;
            if (fsize < 7)
                break;
            fsize = FFMIN(fsize, end - buf2);
            buf2 += fsize;
        }
        max_frames = FFMAX(max_frames, frames);
        if (buf == buf0)
            first_frames = frames;
    }

    if (first_frames >= 3)
        return AVPROBE_SCORE_EXTENSION + 1;
    else if (max_frames > 100)
        return AVPROBE_SCORE_EXTENSION;
    else if (max_frames >= 3)
        return AVPROBE_SCORE_EXTENSION / 2;
    else if (first_frames >= 1)
        return 1;
    else
        return 0;
}

static int adts_aac_resync(AVFormatContext *s)
{
    uint16_t state;
    int64_t start_pos = avio_tell(s->pb);

    // skip data until an ADTS frame is found
    state = avio_r8(s->pb);
    while (!avio_feof(s->pb) &&
           (avio_tell(s->pb) - start_pos) < s->probesize) {
        state = (state << 8) | avio_r8(s->pb);
        if ((state >> 4) != 0xFFF)
            continue;
        avio_seek(s->pb, -2, SEEK_CUR);
        break;
    }
    if (s->pb->eof_reached)
        return AVERROR_EOF;
    if ((state >> 4) != 0xFFF)
        return AVERROR_INVALIDDATA;

    return 0;
}

#ifdef OHOS_OPT_COMPAT
/**
 * ohos.opt.compat.0001
 * fix duration not accurate in aac.
 * There is one packet for every 1024 samples,
 * get the sample num in each frame and sample rate from adts
 * to calculate duration of each frame, then the summation of
 * frame duration is the file duration.
 */
static int adts_aac_get_frame_length(AVFormatContext *s, int64_t offset)
{
    const int adts_header_length_no_crc = 7;
    const int adts_header_length_with_crc = 9;
    uint8_t syncword[2];

    avio_seek(s->pb, offset, SEEK_SET);
    // read syncword
    if (avio_read(s->pb, &syncword, 2) != 2) {
        return 0;
    }
    if ((syncword[0] != 0xff) || ((syncword[1] & 0xf6) != 0xf0)) {
        return 0;
    }

    // read protection_absent
    uint8_t protection_absent;
    avio_seek(s->pb, offset + 1, SEEK_SET);
    if (avio_read(s->pb, &protection_absent, 1) < 1) {
        return 0;
    }
    protection_absent &= 0x1;

    // get frame_size
    uint8_t header[3];
    avio_seek(s->pb, offset + 3, SEEK_SET);
    if (avio_read(s->pb, &header, 3) < 3) {
        return 0;
    }
    int frame_size = (header[0] & 0x3) << 11 | header[1] << 3 | header[2] >> 5;
    // protection_absent is 0 if there is CRC
    int head_size = protection_absent ? adts_header_length_no_crc : adts_header_length_with_crc;
    if (head_size > frame_size) {
        return 0;
    }

    // get adts_buffer_fullness
    uint8_t head[2];
    avio_seek(s->pb, offset + 5, SEEK_SET);
    if (avio_read(s->pb, &head, 2) < 2) {
        return 0;
    }
    uint16_t adts_buffer_fullness = (head[0] & 0x1F) << 6 | (head[1] >> 2);
    if (adts_buffer_fullness != 0x7FF) { // not VBR
        return 0;
    }

    return frame_size;
}

static int adts_aac_get_raw_data_block_num(AVFormatContext *s, int64_t offset)
{
    uint8_t raw_data_block_num = 0;
    avio_seek(s->pb, offset + 6, SEEK_SET);
    if (avio_read(s->pb, &raw_data_block_num, 1) < 1) {
        return 0;
    }
    raw_data_block_num &= 0x3;

    return raw_data_block_num;
}

// get sample rate by index
static uint32_t get_sample_rate(const uint8_t sr_index)
{
    static const uint32_t sample_rates[] =
    {
        96000, 88200, 64000, 48000, 44100, 32000,
        24000, 22050, 16000, 12000, 11025, 8000
    };

    if (sr_index < sizeof(sample_rates) / sizeof(sample_rates[0])) {
        return sample_rates[sr_index];
    }

    return 0;
}

static void adts_aac_get_duration(AVFormatContext *s, AVStream *st)
{
    avio_seek(s->pb, 0, SEEK_SET);
    uint8_t header[2];
    avio_seek(s->pb, 2, SEEK_SET);
    if (avio_read(s->pb, &header, 2) < 2) {
        av_log(NULL, AV_LOG_ERROR, "avio_read header error!\n");
        return;
    }
    int64_t offset = 0;
    // get profile
    uint8_t profile = (header[0] >> 6) & 0x3;
    st->codecpar->profile = profile;

    // get sample rate
    uint8_t sr_index = (header[0] >> 2) & 0xf;
    uint32_t sr = get_sample_rate(sr_index);
    if (sr == 0) {
        av_log(NULL, AV_LOG_ERROR, "adts_aac_read_header read sampletare error!\n");
        return;
    }

    // get channel
    uint8_t channel = (header[0] & 0x1) << 2 | (header[1] >> 6);
    if(channel == 0) {
        av_log(NULL, AV_LOG_ERROR, "adts_aac_read_header read channel error!\n");
        return;
    }

    st->codecpar->channels = channel;
    st->codecpar->sample_rate = sr;
    avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);

    int frame_size = 0;
    int raw_data_block_num = 0;
    int64_t frame_duration_us = 0;
    int64_t duration = 0;
    int64_t frame_num = 0;
    int64_t stream_size = avio_size(s->pb);
    if (stream_size > 0) {
        while (offset < stream_size) {
            if ((frame_size = adts_aac_get_frame_length(s, offset)) == 0) {
                break;
            }
            raw_data_block_num = adts_aac_get_raw_data_block_num(s, offset);
            offset += frame_size;
            frame_num += (raw_data_block_num + 1);
        }
        // round up and get the duration
        frame_duration_us = (1024 * 1000000ll + (sr - 1)) / sr;
        duration = frame_num * frame_duration_us; // us
        duration = av_rescale_q(duration, AV_TIME_BASE_Q, st->time_base);
        if (duration != 0) {
            st->duration = duration;
        }
    }
    avio_seek(s->pb, 0, SEEK_SET);
}
#endif

static int adts_aac_read_header(AVFormatContext *s)
{
    AVStream *st;
    int ret;

    st = avformat_new_stream(s, NULL);
    if (!st)
        return AVERROR(ENOMEM);

    st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
    st->codecpar->codec_id   = s->iformat->raw_codec_id;
    ffstream(st)->need_parsing = AVSTREAM_PARSE_FULL_RAW;

    ff_id3v1_read(s);
    if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
        !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);
    }

    ret = adts_aac_resync(s);
    if (ret < 0)
        return ret;

#ifdef OHOS_OPT_COMPAT
    // ohos.opt.compat.0001
    adts_aac_get_duration(s, st);
#else
    // LCM of all possible ADTS sample rates
    avpriv_set_pts_info(st, 64, 1, 28224000);
#endif

    return 0;
}

static int handle_id3(AVFormatContext *s, AVPacket *pkt)
{
    AVDictionary *metadata = NULL;
    FFIOContext pb;
    ID3v2ExtraMeta *id3v2_extra_meta;
    int ret;

    ret = av_append_packet(s->pb, pkt, ff_id3v2_tag_len(pkt->data) - pkt->size);
    if (ret < 0) {
        return ret;
    }

    ffio_init_context(&pb, pkt->data, pkt->size, 0, NULL, NULL, NULL, NULL);
    ff_id3v2_read_dict(&pb.pub, &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;
}

static int adts_aac_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    int ret, fsize;

retry:
    ret = av_get_packet(s->pb, pkt, ADTS_HEADER_SIZE);
    if (ret < 0)
        return ret;

    if (ret < ADTS_HEADER_SIZE) {
        return AVERROR(EIO);
    }

    if ((AV_RB16(pkt->data) >> 4) != 0xfff) {
        // Parse all the ID3 headers between frames
        int append = ID3v2_HEADER_SIZE - ADTS_HEADER_SIZE;

        av_assert2(append > 0);
        ret = av_append_packet(s->pb, pkt, append);
        if (ret != append) {
            return AVERROR(EIO);
        }
        if (!ff_id3v2_match(pkt->data, ID3v2_DEFAULT_MAGIC)) {
            av_packet_unref(pkt);
            ret = adts_aac_resync(s);
        } else
            ret = handle_id3(s, pkt);
        if (ret < 0)
            return ret;

        goto retry;
    }

    fsize = (AV_RB32(pkt->data + 3) >> 13) & 0x1FFF;
    if (fsize < ADTS_HEADER_SIZE) {
        return AVERROR_INVALIDDATA;
    }

    ret = av_append_packet(s->pb, pkt, fsize - pkt->size);

    return ret;
}

const AVInputFormat ff_aac_demuxer = {
    .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,
    .read_packet  = adts_aac_read_packet,
    .flags        = AVFMT_GENERIC_INDEX,
    .extensions   = "aac",
    .mime_type    = "audio/aac,audio/aacp,audio/x-aac",
    .raw_codec_id = AV_CODEC_ID_AAC,
};