[FFmpeg-devel] [PATCH v2 1/1] avformat: add mca demuxer

liushuyu at aosc.io liushuyu at aosc.io
Thu Sep 3 01:12:19 EEST 2020


On 2020-09-02 00:37, Andreas Rheinhardt wrote:
> liushuyu at aosc.io:
>> From: Zixing Liu <liushuyu at aosc.io>
>> 
>> Signed-off-by: liushuyu <liushuyu at aosc.io>
>> ---
>>  Changelog                |   1 +
>>  doc/general.texi         |   2 +
>>  libavformat/Makefile     |   1 +
>>  libavformat/allformats.c |   1 +
>>  libavformat/mca.c        | 240 
>> +++++++++++++++++++++++++++++++++++++++
>>  libavformat/version.h    |   4 +-
>>  6 files changed, 247 insertions(+), 2 deletions(-)
>>  create mode 100644 libavformat/mca.c
>> 
>> diff --git a/Changelog b/Changelog
>> index 7467e73..ae4219f 100644
>> --- a/Changelog
>> +++ b/Changelog
>> @@ -15,6 +15,7 @@ version <next>:
>>  - Argonaut Games ASF muxer
>>  - AV1 Low overhead bitstream format demuxer
>>  - RPZA video encoder
>> +- MCA demuxer
>> 
>> 
>>  version 4.3:
>> diff --git a/doc/general.texi b/doc/general.texi
>> index d618565..fa76ed4 100644
>> --- a/doc/general.texi
>> +++ b/doc/general.texi
>> @@ -524,6 +524,8 @@ library:
>>      @tab Metadata in text format.
>>  @item MAXIS XA                  @tab   @tab X
>>      @tab Used in Sim City 3000; file extension .xa.
>> + at item MCA                       @tab   @tab X
>> +    @tab Used in some games from Capcom; file extension .mca.
>>  @item MD Studio                 @tab   @tab X
>>  @item Metal Gear Solid: The Twin Snakes @tab @tab X
>>  @item Megalux Frame             @tab   @tab X
>> diff --git a/libavformat/Makefile b/libavformat/Makefile
>> index cbb33fe..7f5ab21 100644
>> --- a/libavformat/Makefile
>> +++ b/libavformat/Makefile
>> @@ -305,6 +305,7 @@ OBJS-$(CONFIG_MATROSKA_MUXER)            += 
>> matroskaenc.o matroska.o \
>>                                              av1.o avc.o hevc.o \
>>                                              flacenc_header.o 
>> avlanguage.o \
>>                                              vorbiscomment.o wv.o
>> +OBJS-$(CONFIG_MCA_DEMUXER)               += mca.o
>>  OBJS-$(CONFIG_MCC_DEMUXER)               += mccdec.o subtitles.o
>>  OBJS-$(CONFIG_MD5_MUXER)                 += hashenc.o
>>  OBJS-$(CONFIG_MGSTS_DEMUXER)             += mgsts.o
>> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
>> index 0aa9dd7..8a71de6 100644
>> --- a/libavformat/allformats.c
>> +++ b/libavformat/allformats.c
>> @@ -232,6 +232,7 @@ extern AVInputFormat  ff_lvf_demuxer;
>>  extern AVInputFormat  ff_lxf_demuxer;
>>  extern AVInputFormat  ff_m4v_demuxer;
>>  extern AVOutputFormat ff_m4v_muxer;
>> +extern AVInputFormat  ff_mca_demuxer;
>>  extern AVInputFormat  ff_mcc_demuxer;
>>  extern AVOutputFormat ff_md5_muxer;
>>  extern AVInputFormat  ff_matroska_demuxer;
>> diff --git a/libavformat/mca.c b/libavformat/mca.c
>> new file mode 100644
>> index 0000000..dbbb374
>> --- /dev/null
>> +++ b/libavformat/mca.c
>> @@ -0,0 +1,240 @@
>> +/*
>> + * MCA demuxer
>> + * Copyright (c) 2020 Zixing Liu
>> + *
>> + * 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 "libavcodec/bytestream.h"
> 
> You don't seem to be using anything from this header.
> 
>> +#include "avformat.h"
>> +#include "internal.h"
>> +
>> +typedef struct MCADemuxContext {
>> +    uint32_t block_count;
>> +    uint16_t block_size;
>> +    uint32_t coef_offset;
>> +    uint32_t current_block;
>> +    uint32_t data_start;
>> +    uint32_t samples_per_block;
>> +} MCADemuxContext;
>> +
>> +static int probe(const AVProbeData *p)
>> +{
>> +    if (AV_RL32(p->buf) == MKTAG('M', 'A', 'D', 'P') &&
>> +        AV_RL16(p->buf + 4) <= 0xff)
>> +        return AVPROBE_SCORE_MAX / 3 * 2;
>> +    return 0;
>> +}
>> +
>> +static int read_header(AVFormatContext *s)
>> +{
>> +    AVStream *st;
>> +    MCADemuxContext *m = s->priv_data;
>> +    int64_t file_size = 0;
>> +    uint16_t version = 0;
>> +    uint32_t header_size, data_size, data_offset, loop_start, 
>> loop_end,
>> +        nb_samples, nb_metadata = 0;
>> +    int ch;
>> +    int ret = AVERROR_EOF;
> 
> This value is never used.
> 
>> +
>> +    st = avformat_new_stream(s, NULL);
>> +    if (!st)
>> +        return AVERROR(ENOMEM);
>> +    st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
> 
> If you used a dedicated variable (common name would be par) to access
> st->codecpar, the lengths of the lines below would not have outliers.
> 
>> +
>> +    // parse file headers
>> +    avio_skip(s->pb, 0x4);      // skip the file magic
>> +    version = avio_rl16(s->pb); // offset 0x4
>> +    avio_skip(s->pb, 0x2);      // padding
>> +    st->codecpar->channels = avio_r8(s->pb);    // offset 0x8
>> +    avio_skip(s->pb, 0x1);      // padding
>> +    m->block_size = avio_rl16(s->pb);   // offset 0xa
>> +    nb_samples = avio_rl32(s->pb);      // offset 0xc
>> +    st->codecpar->sample_rate = avio_rl32(s->pb);       // offset 
>> 0x10
>> +    loop_start = avio_rl32(s->pb);      // offset 0x14
>> +    loop_end = avio_rl32(s->pb);        // offset 0x18
>> +    header_size = avio_rl32(s->pb);     // offset 0x1c
>> +    data_size = avio_rl32(s->pb);       // offset 0x20
>> +    avio_skip(s->pb, 0x4);              // offset 0x24 (duration, 
>> float)
>> +    nb_metadata = avio_rl16(s->pb);     // offset 0x28
>> +    avio_skip(s->pb, 0x2);      // unknown u16 field
> 
> You can align these lines on '=' (well, the lines that have a '='). And
> I don't think that the offset comments are helpful.
> 
>> +
>> +    file_size = avio_size(s->pb);
>> +
> You could directly initialize file_size to this value.
> 
>> +    // samples per frame = 14; frame size = 8 (2^3)
>> +    m->samples_per_block = (m->block_size * 14) >> 3;
>> +    m->block_count = nb_samples / m->samples_per_block;
> 
> You are dividing by zero here if m->samples_per_block is zero. The 
> check
> to rule this out is a few lines below, but that's too late.
> 
>> +    st->duration = nb_samples;
> 
> Is there a reason you prefer this over the duration field you skipped
> earlier?
> 
The duration field I skipped earlier is the duration in seconds (32-bit 
float). This field is missing in some of the files I could find so I 
think it's not very reliable. Also, when seeking the file, I need an 
accurate duration (in the number of samples) to calculate the data 
offset.
>> +
>> +    // sanity checks
>> +    if (!st->codecpar->channels || st->codecpar->sample_rate <= 0
>> +        || m->samples_per_block < 1 || loop_start > loop_end
>> +        || m->block_count < 1)
>> +        return AVERROR_INVALIDDATA;
>> +    if (av_dict_set_int(&s->metadata, "loop_start",
>> +                        av_rescale(loop_start, AV_TIME_BASE,
>> +                                   st->codecpar->sample_rate), 0) < 
>> 0)
>> +        return AVERROR(ENOMEM);
> 
> Just forward the error.
> 
>> +    if (av_dict_set_int(&s->metadata, "loop_end",
>> +                        av_rescale(loop_end, AV_TIME_BASE,
>> +                                   st->codecpar->sample_rate), 0) < 
>> 0)
>> +        return AVERROR(ENOMEM);
>> +    avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
>> +
>> +    if (version <= 4) {
>> +        // version <= 4 needs to use the file size to calculate the 
>> offsets
>> +        if (file_size < 0) {
>> +            return AVERROR(EIO);
>> +        }
>> +        m->data_start = file_size - data_size;
> 
> There is no guarantee here that the right hand side is in the range of
> uint32_t; same goes for data_offset below.
> 
>> +        if (version <= 3) {
>> +            nb_metadata = 0;
>> +            // header_size is not available or incorrect in older 
>> versions
>> +            header_size = m->data_start;
>> +        }
>> +    } else if (version == 5) {
>> +        // read data_start location from the header
>> +        data_offset = header_size - 0x30 * st->codecpar->channels - 
>> 0x4;
>> +        ret = avio_seek(s->pb, data_offset, SEEK_SET);
> 
> ret needs to be an int64_t for it to hold the return value of 
> avio_seek().
> 
>> +        if (ret < 0)
>> +            return ret;
>> +        m->data_start = avio_rl32(s->pb);
>> +        // check if the metadata is reasonable
>> +        if (file_size > 0 && m->data_start + data_size > file_size) {
> 
> The addition will be performed as uint32_t (i.e. with wraparound); same
> for header_size + data_size below.
> 
>> +            // the header is broken beyond repair
>> +            if (header_size + data_size > file_size) {
>> +                av_log(s, AV_LOG_ERROR,
>> +                       "MCA metadata corrupted, unable to determine 
>> the data offset.\n");
>> +                return AVERROR_INVALIDDATA;
>> +            }
>> +            // recover the data_start information from the data size
>> +            av_log(s, AV_LOG_WARNING,
>> +                   "Incorrect header size found in metadata, header 
>> size approximated from the data size\n");
> 
> Split the string in two lines.
> 
>> +            m->data_start = file_size - data_size;
>> +        }
>> +    } else {
>> +        avpriv_request_sample(s, "version %d", version);
>> +        return AVERROR_PATCHWELCOME;
>> +    }
>> +
>> +    // coefficient alignment = 0x30; metadata size = 0x14
>> +    m->coef_offset =
>> +        header_size - 0x30 * st->codecpar->channels + nb_metadata * 
>> 0x14;
> 
> This is a completely local variable; it should not be in the context.
> 
>> +    m->current_block = 0;
> 
> Your context is initially zeroed before read_header.
> 
>> +
>> +    st->start_time = 0;
>> +    st->codecpar->codec_id = AV_CODEC_ID_ADPCM_THP_LE;
>> +
>> +    ret = ff_alloc_extradata(st->codecpar, 32 * 
>> st->codecpar->channels);
>> +    if (ret < 0)
>> +        return ret;
>> +
>> +    ret = avio_seek(s->pb, m->coef_offset, SEEK_SET);
>> +    if (ret < 0)
>> +        return ret;
>> +    for (ch = 0; ch < st->codecpar->channels; ch++) {
>> +        if (avio_read(s->pb, st->codecpar->extradata + ch * 32, 32) 
>> != 32) {
> 
> ffio_read_size().
> 
>> +            return AVERROR_INVALIDDATA;
>> +        }
>> +        // 0x30 (alignment) - 0x20 (actual size, 32) = 0x10 (padding)
>> +        avio_skip(s->pb, 0x10);
>> +    }
>> +
>> +    // seek to the beginning of the adpcm data
>> +    // there are some files that the adpcm audio data is not 
>> immediately after the header
> 
> where the adpcm audio data
> 
>> +    ret = avio_seek(s->pb, m->data_start, SEEK_SET);
>> +    if (ret < 0)
>> +        return ret;
>> +
>> +    return 0;
>> +}
>> +
>> +static int read_packet(AVFormatContext *s, AVPacket *pkt)
>> +{
>> +    AVCodecParameters *par = s->streams[0]->codecpar;
>> +    MCADemuxContext *m = s->priv_data;
>> +    uint32_t samples, size = 0;
>> +    int ret, i = 0;
>> +    uint8_t *dst;
>> +
>> +    if (avio_feof(s->pb))
>> +        return AVERROR_EOF;
>> +    m->current_block++;
>> +    size = m->block_size;
>> +    samples = m->samples_per_block;
>> +    // adapted from brstm.c
>> +    if (m->current_block == m->block_count) {
>> +        if (samples < size * 14 / 8) {
>> +            uint32_t adjusted_size = samples / 14 * 8;
>> +            if (samples % 14)
>> +                adjusted_size += (samples % 14 + 1) / 2 + 1;
>> +
>> +            size = adjusted_size;
>> +        }
>> +    } else if (m->current_block > m->block_count)
>> +        return AVERROR_EOF;
>> +
>> +    if (size > (INT_MAX - 32 - 4) ||
>> +        (32 + 4 + size) > (INT_MAX / par->channels) ||
>> +        (32 + 4 + size) * par->channels > INT_MAX - 8)
>> +        return AVERROR_INVALIDDATA;
> 
> You should check the block_size when reading the header to rule this 
> out.
> 
>> +    if ((ret = av_new_packet(pkt, size * par->channels)) < 0)
>> +        return ret;
>> +    dst = pkt->data;
>> +    for (i = 0; i < par->channels; i++) {
>> +        ret = avio_read(s->pb, dst, size);
>> +        dst += size;
>> +        if (ret != size) {
>> +            return AVERROR(EIO);
>> +        }
>> +    }
> 
> There is really no need to read the data for each channel individually;
> the whole thing above can be replaced with av_get_packet().
> 
>> +    pkt->duration = samples;
>> +    pkt->stream_index = 0;
>> +
>> +    return ret;
> 
> return 0 on success (ret currently contains size).
> 
>> +}
>> +
>> +static int read_seek(AVFormatContext *s, int stream_index,
>> +                     int64_t timestamp, int flags)
>> +{
>> +    AVStream *st = s->streams[stream_index];
>> +    MCADemuxContext *m = s->priv_data;
>> +    int64_t ret = 0;
>> +
>> +    timestamp /= m->samples_per_block;
>> +    ret = avio_seek(s->pb, m->data_start + timestamp * m->block_size 
>> *
>> +                    st->codecpar->channels, SEEK_SET);
>> +
>> +    if (ret < 0)
>> +        return ret;
>> +
>> +    m->current_block = timestamp;
>> +    ff_update_cur_dts(s, st, timestamp * m->samples_per_block);
>> +    return 0;
>> +}
>> +
>> +AVInputFormat ff_mca_demuxer = {
>> +    .name           = "mca",
>> +    .long_name      = NULL_IF_CONFIG_SMALL("MCA Audio Format"),
>> +    .priv_data_size = sizeof(MCADemuxContext),
>> +    .read_probe     = probe,
>> +    .read_header    = read_header,
>> +    .read_packet    = read_packet,
>> +    .read_seek      = read_seek,
>> +    .extensions     = "mca",
>> +};
>> diff --git a/libavformat/version.h b/libavformat/version.h
>> index 88876ae..146db09 100644
>> --- a/libavformat/version.h
>> +++ b/libavformat/version.h
>> @@ -32,8 +32,8 @@
>>  // Major bumping may affect Ticket5467, 5421, 5451(compatibility with 
>> Chromium)
>>  // Also please add any ticket numbers that you believe might be 
>> affected here
>>  #define LIBAVFORMAT_VERSION_MAJOR  58
>> -#define LIBAVFORMAT_VERSION_MINOR  51
>> -#define LIBAVFORMAT_VERSION_MICRO 101
>> +#define LIBAVFORMAT_VERSION_MINOR  52
>> +#define LIBAVFORMAT_VERSION_MICRO 100
>> 
>>  #define LIBAVFORMAT_VERSION_INT 
>> AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
>>                                                 
>> LIBAVFORMAT_VERSION_MINOR, \
>> 
> 
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I will fix all the issues you have proposed so far. And thanks for such 
a detailed review!

Thanks,
Zixing


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