[FFmpeg-devel] [PATCH v2 2/2] avcodec: add a ffv1 parser

[James Almer]

On 2/3/2025 2:42 AM, Lynne wrote:
> On 03/02/2025 03:16, James Almer wrote:
>> Only setting frame and stream properties. No packetization is performed.
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>   configure                |  1 +
>>   libavcodec/Makefile      |  1 +
>>   libavcodec/ffv1_parser.c | 86 ++++++++++++++++++++++++++++++++++++++++
>>   libavcodec/parsers.c     |  1 +
>>   4 files changed, 89 insertions(+)
>>   create mode 100644 libavcodec/ffv1_parser.c
>>
>> diff --git a/configure b/configure
>> index 06f641ead0..f09faaf505 100755
>> --- a/configure
>> +++ b/configure
>> @@ -3469,6 +3469,7 @@ vvc_qsv_decoder_select="vvc_mp4toannexb_bsf qsvdec"
>>   aac_parser_select="adts_header mpeg4audio"
>>   av1_parser_select="cbs_av1"
>>   evc_parser_select="evcparse"
>> +ffv1_parser_select="rangecoder"
>>   ftr_parser_select="adts_header mpeg4audio"
>>   h264_parser_select="golomb h264dsp h264parse h264_sei"
>>   hevc_parser_select="hevcparse hevc_sei"
>> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
>> index 44bb34182a..973e2c45d6 100644
>> --- a/libavcodec/Makefile
>> +++ b/libavcodec/Makefile
>> @@ -1207,6 +1207,7 @@ OBJS-$(CONFIG_DVBSUB_PARSER)           += 
>> dvbsub_parser.o
>>   OBJS-$(CONFIG_DVD_NAV_PARSER)          += dvd_nav_parser.o
>>   OBJS-$(CONFIG_DVDSUB_PARSER)           += dvdsub_parser.o
>>   OBJS-$(CONFIG_EVC_PARSER)              += evc_parser.o
>> +OBJS-$(CONFIG_FFV1_PARSER)             += ffv1_parser.o ffv1_parse.o 
>> ffv1.o
>>   OBJS-$(CONFIG_FLAC_PARSER)             += flac_parser.o flacdata.o 
>> flac.o
>>   OBJS-$(CONFIG_FTR_PARSER)              += ftr_parser.o
>>   OBJS-$(CONFIG_G723_1_PARSER)           += g723_1_parser.o
>> diff --git a/libavcodec/ffv1_parser.c b/libavcodec/ffv1_parser.c
>> new file mode 100644
>> index 0000000000..d0b396b693
>> --- /dev/null
>> +++ b/libavcodec/ffv1_parser.c
>> @@ -0,0 +1,86 @@
>> +/*
>> + * 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 "avcodec.h"
>> +#include "ffv1.h"
>> +#include "rangecoder.h"
>> +
>> +typedef struct FFV1ParseContext {
>> +    FFV1Context f;
>> +    int got_first;
>> +} FFV1ParseContext;
>> +
>> +static int parse(AVCodecParserContext *s,
>> +                 AVCodecContext *avctx,
>> +                 const uint8_t **poutbuf, int *poutbuf_size,
>> +                 const uint8_t *buf, int buf_size)
>> +{
>> +    FFV1ParseContext *p = s->priv_data;
>> +    FFV1Context *f = &p->f;
>> +    RangeCoder c;
>> +    uint8_t keystate = 128;
>> +
>> +    *poutbuf      = buf;
>> +    *poutbuf_size = buf_size;
>> +
>> +    if (!p->got_first) {
>> +        int ret = ff_ffv1_common_init(avctx, f);
>> +        p->got_first = 1;
>> +        if (ret < 0)
>> +            return buf_size;
>> +
>> +        if (avctx->extradata_size > 0 && (ret = 
>> ff_ffv1_read_extra_header(f)) < 0)
>> +            return buf_size;
>> +    }
>> +
>> +    ff_init_range_decoder(&c, buf, buf_size);
>> +    ff_build_rac_states(&c, 0.05 * (1LL << 32), 256 - 8);
>> +
>> +    f->avctx = avctx;
>> +    s->key_frame = get_rac(&c, &keystate);
>> +    s->pict_type = AV_PICTURE_TYPE_I; //FIXME I vs. P, see ffv1dec.c
>> +    s->field_order = AV_FIELD_UNKNOWN;
>> +    s->picture_structure = AV_PICTURE_STRUCTURE_UNKNOWN;
>> +
>> +    if (s->key_frame) {
>> +        uint8_t state[CONTEXT_SIZE];
>> +        memset(state, 128, sizeof(state));
>> +        ff_ffv1_parse_header(f, &c, state);
>> +    }
>> +
>> +    s->width  = f->width;
>> +    s->height = f->height;
>> +    s->format = f->pix_fmt;
>> +
>> +    return buf_size;
>> +}
>> +
>> +static void close(AVCodecParserContext *s)
>> +{
>> +    FFV1ParseContext *p = s->priv_data;
>> +
>> +    p->f.avctx = NULL;
> 
> Since avctx looks like is only used for logging now in parse_header, you 
> could cast AVCodecParserContext and avoid av_log(NULL)s on error.

parse_header also sets and reads bits_per_raw_sample in avctx, so it's 
not just a log context. And avctx being set to null here is only a 
precaution, because ff_ffv1_close() doesn't currently access it.

> 
> Other than that, patchset looks good to me, thanks.

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