[FFmpeg-devel] [PATCH 2/2] avformat: add demuxer for Rayman 2's APM format

Zane van Iperen zane at zanevaniperen.com
Mon Feb 17 11:49:52 EET 2020


On 17/2/20 7:26 pm, Paul B Mahol wrote:
> 
> On 2/17/20, Zane van Iperen <zane at zanevaniperen.com> wrote:
>> Adds support for the APM file format used by Ubisoft's Rayman 2.
>>
>> Signed-off-by: Zane van Iperen <zane at zanevaniperen.com>
>> ---
>>   libavformat/Makefile     |   1 +
>>   libavformat/allformats.c |   1 +
>>   libavformat/apm.c        | 171 +++++++++++++++++++++++++++++++++++++++
>>   libavformat/version.h    |   2 +-
>>   4 files changed, 174 insertions(+), 1 deletion(-)
>>   create mode 100644 libavformat/apm.c
>>
>> diff --git a/libavformat/Makefile b/libavformat/Makefile
>> index a9972fd99a..e0681058a2 100644
>> --- a/libavformat/Makefile
>> +++ b/libavformat/Makefile
>> @@ -92,6 +92,7 @@ OBJS-$(CONFIG_AMRWB_DEMUXER)             += amr.o
>>   OBJS-$(CONFIG_ANM_DEMUXER)               += anm.o
>>   OBJS-$(CONFIG_APC_DEMUXER)               += apc.o
>>   OBJS-$(CONFIG_APE_DEMUXER)               += ape.o apetag.o img2.o
>> +OBJS-$(CONFIG_APM_DEMUXER)               += apm.o
>>   OBJS-$(CONFIG_APNG_DEMUXER)              += apngdec.o
>>   OBJS-$(CONFIG_APNG_MUXER)                += apngenc.o
>>   OBJS-$(CONFIG_APTX_DEMUXER)              += aptxdec.o rawdec.o
>> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
>> index 3ea4100e85..0209bf0e30 100644
>> --- a/libavformat/allformats.c
>> +++ b/libavformat/allformats.c
>> @@ -53,6 +53,7 @@ extern AVInputFormat  ff_amrwb_demuxer;
>>   extern AVInputFormat  ff_anm_demuxer;
>>   extern AVInputFormat  ff_apc_demuxer;
>>   extern AVInputFormat  ff_ape_demuxer;
>> +extern AVInputFormat  ff_apm_demuxer;
>>   extern AVInputFormat  ff_apng_demuxer;
>>   extern AVOutputFormat ff_apng_muxer;
>>   extern AVInputFormat  ff_aptx_demuxer;
>> diff --git a/libavformat/apm.c b/libavformat/apm.c
>> new file mode 100644
>> index 0000000000..d13c2eda31
>> --- /dev/null
>> +++ b/libavformat/apm.c
>> @@ -0,0 +1,171 @@
>> +/*
>> + * Rayman 2 APM Demuxer
>> + *
>> + * Copyright (C) 2020 Zane van Iperen (zane at zanevaniperen.com)
>> + *
>> + * 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 "avformat.h"
>> +#include "internal.h"
>> +#include "riff.h"
>> +#include "libavutil/internal.h"
>> +#include "libavutil/intreadwrite.h"
>> +
>> +#define APM_FILE_HEADER_SIZE    20
>> +#define APM_VS12_CHUNK_SIZE     76
>> +#define APM_MAX_READ_SIZE       4096
>> +
>> +typedef struct APMState {
>> +    int32_t     has_saved;
>> +    int32_t     predictor_r;
>> +    int32_t     step_index_r;
>> +    int32_t     saved_r;
>> +    int32_t     predictor_l;
>> +    int32_t     step_index_l;
>> +    int32_t     saved_l;
>> +} APMState;
>> +
>> +typedef struct APMVS12Chunk {
>> +    uint32_t    magic;
>> +    uint32_t    file_size;
>> +    uint32_t    data_size;
>> +    uint32_t    unk1;
>> +    uint32_t    unk2;
>> +    APMState    state;
>> +    uint32_t    pad[7];
>> +} APMVS12Chunk;
>> +
>> +static void apm_parse_vs12(APMVS12Chunk *vs12, const uint8_t *buf)
>> +{
>> +    vs12->magic                 = AV_RL32(buf + 0);
>> +    vs12->file_size             = AV_RL32(buf + 4);
>> +    vs12->data_size             = AV_RL32(buf + 8);
>> +    vs12->unk1                  = AV_RL32(buf + 12);
>> +    vs12->unk2                  = AV_RL32(buf + 16);
>> +
>> +    vs12->state.has_saved       = AV_RL32(buf + 20);
>> +    vs12->state.predictor_r     = AV_RL32(buf + 24);
>> +    vs12->state.step_index_r    = AV_RL32(buf + 28);
>> +    vs12->state.saved_r         = AV_RL32(buf + 32);
>> +    vs12->state.predictor_l     = AV_RL32(buf + 36);
>> +    vs12->state.step_index_l    = AV_RL32(buf + 40);
>> +    vs12->state.saved_l         = AV_RL32(buf + 44);
>> +
>> +    for (int i = 0; i < FF_ARRAY_ELEMS(vs12->pad); i++)
>> +        vs12->pad[i]            = AV_RL32(buf + 48 + (i * 4));
>> +}
>> +
>> +static int apm_read_header(AVFormatContext *s)
>> +{
>> +    int64_t ret;
>> +    AVStream *st;
>> +    APMVS12Chunk vs12;
>> +    uint8_t buf[APM_VS12_CHUNK_SIZE];
>> +
>> +    if (!(st = avformat_new_stream(s, NULL)))
>> +        return AVERROR(ENOMEM);
>> +
>> +    /* The header starts with a WAVEFORMATEX */
>> +    if ((ret = ff_get_wav_header(s, s->pb, st->codecpar,
>> APM_FILE_HEADER_SIZE, 0)) < 0)
>> +        return ret;
>> +
>> +    if (st->codecpar->bits_per_coded_sample != 4)
>> +        return AVERROR_INVALIDDATA;
>> +
>> +    if (st->codecpar->codec_tag != 0x2000)
>> +        return AVERROR_INVALIDDATA;
>> +
>> +    /* ff_get_wav_header() does most of the work, but we need to fix a few
>> things. */
>> +    st->codecpar->codec_id              = AV_CODEC_ID_ADPCM_IMA_APM;
>> +    st->codecpar->codec_tag             = 0;
>> +
>> +    if (st->codecpar->channels == 2)
>> +        st->codecpar->channel_layout    = AV_CH_LAYOUT_STEREO;
>> +    else if (st->codecpar->channels == 1)
>> +        st->codecpar->channel_layout    = AV_CH_LAYOUT_MONO;
>> +    else
>> +        return AVERROR_INVALIDDATA;
>> +
>> +    st->codecpar->format                = AV_SAMPLE_FMT_S16P;
>> +    st->codecpar->bits_per_raw_sample   = 16;
>> +    st->codecpar->bit_rate              = st->codecpar->channels *
>> +                                          st->codecpar->sample_rate *
>> +
>> st->codecpar->bits_per_coded_sample;
>> +
>> +    if ((ret = avio_read(s->pb, buf, APM_VS12_CHUNK_SIZE)) < 0)
>> +        return ret;
>> +    else if (ret != APM_VS12_CHUNK_SIZE)
>> +        return AVERROR(EIO);
>> +
>> +    apm_parse_vs12(&vs12, buf);
>> +
>> +    if (vs12.magic != MKTAG('v', 's', '1', '2')) {
>> +        return AVERROR_INVALIDDATA;
>> +    }
>> +
>> +    if (vs12.state.has_saved) {
>> +        avpriv_request_sample(s, "Saved Samples");
>> +        return AVERROR_PATCHWELCOME;
>> +    }
>> +
>> +    if (avio_rl32(s->pb) != MKTAG('D', 'A', 'T', 'A'))
>> +        return AVERROR_INVALIDDATA;
>> +
>> +    if ((ret = ff_alloc_extradata(st->codecpar, 16)) < 0)
>> +        return ret;
>> +
>> +    AV_WN32(st->codecpar->extradata +  0, vs12.state.predictor_l);
>> +    AV_WN32(st->codecpar->extradata +  4, vs12.state.step_index_l);
>> +    AV_WN32(st->codecpar->extradata +  8, vs12.state.predictor_r);
>> +    AV_WN32(st->codecpar->extradata + 12, vs12.state.step_index_r);
> 
> Use same endianess as it is written in file.
> 

Fixed (and in the codec too).

>> +
>> +    avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
>> +    st->start_time  = 0;
>> +    st->duration    = vs12.data_size *
>> +                      (8 / st->codecpar->bits_per_coded_sample) /
>> +                      st->codecpar->channels;
>> +    return 0;
>> +}
>> +
>> +static int apm_read_packet(AVFormatContext *s, AVPacket *pkt)
>> +{
>> +    int ret;
>> +    AVCodecParameters *par = s->streams[0]->codecpar;
>> +
>> +    /*
>> +     * For future reference: if files with the `has_saved` field set ever
>> +     * surface, `saved_l`, and `saved_r` will each contain 8 "saved"
>> samples
>> +     * that should be sent to the decoder before the actual data.
>> +     */
>> +
>> +    if ((ret = av_get_packet(s->pb, pkt, APM_MAX_READ_SIZE)) < 0)
>> +        return ret;
>> +
>> +    pkt->flags          &= ~AV_PKT_FLAG_CORRUPT;
>> +    pkt->stream_index   = 0;
>> +    pkt->duration       = ret * (8 / par->bits_per_coded_sample) /
>> par->channels;
>> +
>> +    return 0;
>> +}
>> +
>> +AVInputFormat ff_apm_demuxer = {
>> +    .name           = "apm",
>> +    .long_name      = NULL_IF_CONFIG_SMALL("Ubisoft Rayman 2 APM"),
>> +    .read_header    = apm_read_header,
>> +    .read_packet    = apm_read_packet,
>> +    .extensions     = "apm"
> 
> Also add probe function.

There's no real "magic" fields to look for, hence why I set the `extensions`
field. What would a probe function do in this case?

> 
>> +};
>> diff --git a/libavformat/version.h b/libavformat/version.h
>> index 94fa57614d..4724269b3c 100644
>> --- a/libavformat/version.h
>> +++ b/libavformat/version.h
>> @@ -32,7 +32,7 @@
>>   // 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  38
>> +#define LIBAVFORMAT_VERSION_MINOR  39
>>   #define LIBAVFORMAT_VERSION_MICRO 101
> 
> Reset micro to 0, when changing minor.
> 
> 

Gah, knew I'd forgotten something simple. Fixed.

>>
>>   #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
>> --
>> 2.17.1
>>
>>
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Zane



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