Re: [FFmpeg-devel] [PATCH 2/6] lavf: APV demuxer

[Mark Thompson <sw@jkqxz.net>]

On 21/04/2025 01:54, Michael Niedermayer wrote:
> On Sat, Apr 19, 2025 at 08:07:00PM +0100, Mark Thompson wrote:
>> Demuxes raw streams as defined in draft spec section 10.2.
>> ---
>>  libavformat/Makefile     |   1 +
>>  libavformat/allformats.c |   1 +
>>  libavformat/apvdec.c     | 245 +++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 247 insertions(+)
>>  create mode 100644 libavformat/apvdec.c
>>
>> diff --git a/libavformat/Makefile b/libavformat/Makefile
>> index a94ac66e7e..ef96c2762e 100644
>> --- a/libavformat/Makefile
>> +++ b/libavformat/Makefile
>> @@ -119,6 +119,7 @@ OBJS-$(CONFIG_APTX_DEMUXER)              += aptxdec.o
>>  OBJS-$(CONFIG_APTX_MUXER)                += rawenc.o
>>  OBJS-$(CONFIG_APTX_HD_DEMUXER)           += aptxdec.o
>>  OBJS-$(CONFIG_APTX_HD_MUXER)             += rawenc.o
>> +OBJS-$(CONFIG_APV_DEMUXER)               += apvdec.o
>>  OBJS-$(CONFIG_AQTITLE_DEMUXER)           += aqtitledec.o subtitles.o
>>  OBJS-$(CONFIG_ARGO_ASF_DEMUXER)          += argo_asf.o
>>  OBJS-$(CONFIG_ARGO_ASF_MUXER)            += argo_asf.o
>> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
>> index 445f13f42a..90a4fe64ec 100644
>> --- a/libavformat/allformats.c
>> +++ b/libavformat/allformats.c
>> @@ -72,6 +72,7 @@ extern const FFInputFormat  ff_aptx_demuxer;
>>  extern const FFOutputFormat ff_aptx_muxer;
>>  extern const FFInputFormat  ff_aptx_hd_demuxer;
>>  extern const FFOutputFormat ff_aptx_hd_muxer;
>> +extern const FFInputFormat  ff_apv_demuxer;
>>  extern const FFInputFormat  ff_aqtitle_demuxer;
>>  extern const FFInputFormat  ff_argo_asf_demuxer;
>>  extern const FFOutputFormat ff_argo_asf_muxer;
>> diff --git a/libavformat/apvdec.c b/libavformat/apvdec.c
>> new file mode 100644
>> index 0000000000..008cbef708
>> --- /dev/null
>> +++ b/libavformat/apvdec.c
>> @@ -0,0 +1,245 @@
>> +/*
>> + * 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 "libavcodec/apv.h"
> 
> missing file

I will reorder the cbs patch before this one.

>> +#include "libavcodec/get_bits.h"
>> +#include "avformat.h"
>> +#include "avio_internal.h"
>> +#include "demux.h"
>> +#include "internal.h"
>> +
>> +
>> +#define APV_TAG MKBETAG('a', 'P', 'v', '1')
>> +
>> +typedef struct APVHeaderInfo {
>> +    uint8_t  pbu_type;
>> +    uint16_t group_id;
>> +
>> +    uint8_t  profile_idc;
>> +    uint8_t  level_idc;
>> +    uint8_t  band_idc;
>> +
>> +    uint32_t frame_width;
>> +    uint32_t frame_height;
>> +
>> +    uint8_t  chroma_format_idc;
>> +    uint8_t  bit_depth_minus8;
>> +
>> +    enum AVPixelFormat pixel_format;
>> +} APVHeaderInfo;
>> +
>> +static const enum AVPixelFormat apv_format_table[5][5] = {
>> +    { AV_PIX_FMT_GRAY8,    AV_PIX_FMT_GRAY10,     AV_PIX_FMT_GRAY12,     AV_PIX_FMT_GRAY14, AV_PIX_FMT_GRAY16 },
>> +    { 0 }, // 4:2:0 is not valid.
>> +    { AV_PIX_FMT_YUV422P,  AV_PIX_FMT_YUV422P10,  AV_PIX_FMT_YUV422P12,  AV_PIX_FMT_GRAY14, AV_PIX_FMT_YUV422P16 },
>> +    { AV_PIX_FMT_YUV444P,  AV_PIX_FMT_YUV444P10,  AV_PIX_FMT_YUV444P12,  AV_PIX_FMT_GRAY14, AV_PIX_FMT_YUV444P16 },
>> +    { AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUVA444P10, AV_PIX_FMT_YUVA444P12, AV_PIX_FMT_GRAY14, AV_PIX_FMT_YUVA444P16 },
>> +};
>> +
> 
>> +static int apv_extract_header_info(APVHeaderInfo *info,
>> +                                   GetBitContext *gbc)
>> +{
>> +    int zero, bit_depth_index;
>> +
>> +    info->pbu_type = get_bits(gbc, 8);
>> +    info->group_id = get_bits(gbc, 16);
>> +
>> +    zero = get_bits(gbc, 8);
>> +    if (zero != 0)
>> +        return 0;
> 
> this should use negative AVERROR* for errors for consistency

Ok.

>> +
>> +    if (info->pbu_type != APV_PBU_PRIMARY_FRAME)
>> +        return 0;
>> +
>> +    info->profile_idc = get_bits(gbc, 8);
>> +    info->level_idc   = get_bits(gbc, 8);
>> +    info->band_idc    = get_bits(gbc, 3);
>> +
>> +    zero = get_bits(gbc, 5);
>> +    if (zero != 0)
>> +        return 0;
>> +
> 
>> +    info->frame_width  = get_bits(gbc, 24);
>> +    info->frame_height = get_bits(gbc, 24);
> 
> frame_width and frame_height would be better as int instead of uint32_t
> given its only 24bit
> 
> its also more consistent
> git grep 'int *width' | wc
>    1935   15372  180444
> 
> git grep 'uint32_t *width' | wc
>      15      62     740

Sure.  We can change it to uint32_t later if there is a decision to use APVDecoderConfigurationRecord directly.

> [...]
>> +static int apv_probe(const AVProbeData *p)
>> +{
>> +    GetBitContext gbc;
>> +    APVHeaderInfo header;
>> +    uint32_t au_size, tag, pbu_size;
>> +    int score = AVPROBE_SCORE_EXTENSION + 1;
>> +    int ret;
>> +
>> +    init_get_bits8(&gbc, p->buf, p->buf_size);
>> +
>> +    au_size = get_bits_long(&gbc, 32);
>> +    if (au_size < 16) {

Here ^

>> +        // Too small.
>> +        return 0;
>> +    }
>> +    // The spec doesn't have this tag, but the reference software and
>> +    // all current files do.  Treat it as optional and skip if present,
>> +    // but if it is there then this is definitely an APV file.
>> +    tag = get_bits_long(&gbc, 32);
>> +    if (tag == APV_TAG) {
>> +        pbu_size = get_bits_long(&gbc, 32);
>> +        score = AVPROBE_SCORE_MAX;
>> +    } else {
>> +        pbu_size = tag;
>> +    }
>> +    if (pbu_size < 16) {
>> +        // Too small.
>> +        return 0;
>> +    }
>> +
>> +    ret = apv_extract_header_info(&header, &gbc);
> 
> something somewhere should check buf_size or size in gbc
> otherwise a truncated header would be accepted

See check above.

Thanks,

- Mark

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