Re: [FFmpeg-devel] [PATCH] lavc: add null codecs

[Paul B Mahol <onemda@gmail.com>]

On 1/27/23, Anton Khirnov <anton@khirnov.net> wrote:
> They discard all input without ever returning any output. Useful for
> development.
> ---
>  libavcodec/Makefile     |  4 ++
>  libavcodec/allcodecs.c  |  6 +++
>  libavcodec/codec_desc.c | 12 ++++++
>  libavcodec/codec_id.h   | 10 +++++
>  libavcodec/null.c       | 96 +++++++++++++++++++++++++++++++++++++++++
>  libavcodec/version.h    |  2 +-
>  6 files changed, 129 insertions(+), 1 deletion(-)
>  create mode 100644 libavcodec/null.c
>
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index 2d9710923d..098ab18353 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -219,6 +219,8 @@ OBJS-$(CONFIG_AMRWB_DECODER)           += amrwbdec.o
> celp_filters.o   \
>                                            acelp_pitch_delay.o
>  OBJS-$(CONFIG_AMV_ENCODER)             += mjpegenc.o mjpegenc_common.o
>  OBJS-$(CONFIG_ANM_DECODER)             += anm.o
> +OBJS-$(CONFIG_ANULL_DECODER)           += null.o
> +OBJS-$(CONFIG_ANULL_ENCODER)           += null.o
>  OBJS-$(CONFIG_ANSI_DECODER)            += ansi.o cga_data.o
>  OBJS-$(CONFIG_APAC_DECODER)            += apac.o
>  OBJS-$(CONFIG_APE_DECODER)             += apedec.o
> @@ -746,6 +748,8 @@ OBJS-$(CONFIG_VCR1_DECODER)            += vcr1.o
>  OBJS-$(CONFIG_VMDAUDIO_DECODER)        += vmdaudio.o
>  OBJS-$(CONFIG_VMDVIDEO_DECODER)        += vmdvideo.o
>  OBJS-$(CONFIG_VMNC_DECODER)            += vmnc.o
> +OBJS-$(CONFIG_VNULL_DECODER)           += null.o
> +OBJS-$(CONFIG_VNULL_ENCODER)           += null.o
>  OBJS-$(CONFIG_VORBIS_DECODER)          += vorbisdec.o vorbisdsp.o vorbis.o
> \
>                                            vorbis_data.o
>  OBJS-$(CONFIG_VORBIS_ENCODER)          += vorbisenc.o vorbis.o \
> diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
> index f728c6c82e..7452002f24 100644
> --- a/libavcodec/allcodecs.c
> +++ b/libavcodec/allcodecs.c
> @@ -882,6 +882,12 @@ extern const FFCodec ff_vp9_qsv_decoder;
>  extern const FFCodec ff_vp9_vaapi_encoder;
>  extern const FFCodec ff_vp9_qsv_encoder;
>
> +// null codecs
> +extern const FFCodec ff_vnull_decoder;
> +extern const FFCodec ff_vnull_encoder;
> +extern const FFCodec ff_anull_decoder;
> +extern const FFCodec ff_anull_encoder;
> +
>  // The iterate API is not usable with ossfuzz due to the excessive size of
> binaries created
>  #if CONFIG_OSSFUZZ
>  const FFCodec * codec_list[] = {
> diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
> index 2272232ed6..b3bec2f659 100644
> --- a/libavcodec/codec_desc.c
> +++ b/libavcodec/codec_desc.c
> @@ -1923,6 +1923,12 @@ static const AVCodecDescriptor codec_descriptors[] =
> {
>          .long_name = NULL_IF_CONFIG_SMALL("ViewQuest VQC"),
>          .props     = AV_CODEC_PROP_LOSSY,
>      },
> +    {
> +        .id        = AV_CODEC_ID_VNULL,
> +        .type      = AVMEDIA_TYPE_VIDEO,
> +        .name      = "vnull",
> +        .long_name = NULL_IF_CONFIG_SMALL("Null video codec"),
> +    },
>
>      /* various PCM "codecs" */
>      {
> @@ -3339,6 +3345,12 @@ static const AVCodecDescriptor codec_descriptors[] =
> {
>          .long_name = NULL_IF_CONFIG_SMALL("FTR Voice"),
>          .props     = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
>      },
> +    {
> +        .id        = AV_CODEC_ID_ANULL,
> +        .type      = AVMEDIA_TYPE_AUDIO,
> +        .name      = "anull",
> +        .long_name = NULL_IF_CONFIG_SMALL("Null audio codec"),
> +    },
>
>      /* subtitle codecs */
>      {
> diff --git a/libavcodec/codec_id.h b/libavcodec/codec_id.h
> index 5ec3fd4b30..c197e956b7 100644
> --- a/libavcodec/codec_id.h
> +++ b/libavcodec/codec_id.h
> @@ -320,6 +320,11 @@ enum AVCodecID {
>      AV_CODEC_ID_WBMP,
>      AV_CODEC_ID_MEDIA100,
>      AV_CODEC_ID_VQC,
> +    /**
> +     * Dummy null video codec, useful mainly for development and
> debugging.
> +     * Null encoder/decoder discard all input and never return any output.
> +     */
> +    AV_CODEC_ID_VNULL,

Cant you move those two to special ones like wrapped avframe?

With that one changed LGTM.

>
>      /* various PCM "codecs" */
>      AV_CODEC_ID_FIRST_AUDIO = 0x10000,     ///< A dummy id pointing at the
> start of audio codecs
> @@ -534,6 +539,11 @@ enum AVCodecID {
>      AV_CODEC_ID_MISC4,
>      AV_CODEC_ID_APAC,
>      AV_CODEC_ID_FTR,
> +    /**
> +     * Dummy null audio codec, useful mainly for development and
> debugging.
> +     * Null encoder/decoder discard all input and never return any output.
> +     */
> +    AV_CODEC_ID_ANULL,
>
>      /* subtitle codecs */
>      AV_CODEC_ID_FIRST_SUBTITLE = 0x17000,          ///< A dummy ID pointing
> at the start of subtitle codecs.
> diff --git a/libavcodec/null.c b/libavcodec/null.c
> new file mode 100644
> index 0000000000..df75a077ae
> --- /dev/null
> +++ b/libavcodec/null.c
> @@ -0,0 +1,96 @@
> +/*
> + * Null codecs
> + *
> + * 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 "config_components.h"
> +
> +#include "codec_internal.h"
> +#include "decode.h"
> +#include "encode.h"
> +
> +#if CONFIG_VNULL_DECODER || CONFIG_ANULL_DECODER
> +static int null_decode(AVCodecContext *avctx, AVFrame *frame,
> +                       int *got_frame, AVPacket *avpkt)
> +{
> +    *got_frame = 0;
> +    return avpkt->size;
> +}
> +
> +#if CONFIG_VNULL_DECODER
> +const FFCodec ff_vnull_decoder = {
> +    .p.name         = "vnull",
> +    CODEC_LONG_NAME("null video"),
> +    .p.type         = AVMEDIA_TYPE_VIDEO,
> +    .p.id           = AV_CODEC_ID_VNULL,
> +    .p.capabilities = AV_CODEC_CAP_DR1,
> +    FF_CODEC_DECODE_CB(null_decode),
> +};
> +#endif
> +
> +#if CONFIG_ANULL_DECODER
> +const FFCodec ff_anull_decoder = {
> +    .p.name         = "anull",
> +    CODEC_LONG_NAME("null audio"),
> +    .p.type         = AVMEDIA_TYPE_AUDIO,
> +    .p.id           = AV_CODEC_ID_ANULL,
> +    .p.capabilities = AV_CODEC_CAP_DR1,
> +    FF_CODEC_DECODE_CB(null_decode),
> +};
> +#endif
> +
> +#endif
> +
> +#if CONFIG_VNULL_ENCODER || CONFIG_ANULL_ENCODER
> +static int null_encode(AVCodecContext *avctx, AVPacket *pkt,
> +                       const AVFrame *frame, int *got_packet)
> +{
> +    *got_packet = 0;
> +    return 0;
> +}
> +
> +#if CONFIG_VNULL_ENCODER
> +const FFCodec ff_vnull_encoder = {
> +    .p.name         = "vnull",
> +    CODEC_LONG_NAME("null video"),
> +    .p.type         = AVMEDIA_TYPE_VIDEO,
> +    .p.id           = AV_CODEC_ID_VNULL,
> +    FF_CODEC_ENCODE_CB(null_encode),
> +};
> +#endif
> +
> +#if CONFIG_ANULL_ENCODER
> +const FFCodec ff_anull_encoder = {
> +    .p.name         = "anull",
> +    CODEC_LONG_NAME("null audio"),
> +    .p.type         = AVMEDIA_TYPE_AUDIO,
> +    .p.id           = AV_CODEC_ID_ANULL,
> +    .p.capabilities = AV_CODEC_CAP_VARIABLE_FRAME_SIZE,
> +    .p.sample_fmts  = (const enum AVSampleFormat[]){
> +        AV_SAMPLE_FMT_U8,  AV_SAMPLE_FMT_U8P,
> +        AV_SAMPLE_FMT_S16, AV_SAMPLE_FMT_S16P,
> +        AV_SAMPLE_FMT_S32, AV_SAMPLE_FMT_S32P,
> +        AV_SAMPLE_FMT_S64, AV_SAMPLE_FMT_S64P,
> +        AV_SAMPLE_FMT_FLT, AV_SAMPLE_FMT_FLTP,
> +        AV_SAMPLE_FMT_DBL, AV_SAMPLE_FMT_DBLP,
> +    },
> +    FF_CODEC_ENCODE_CB(null_encode),
> +};
> +#endif
> +
> +#endif
> diff --git a/libavcodec/version.h b/libavcodec/version.h
> index dfd3d5d7e5..7ac8d2b2fe 100644
> --- a/libavcodec/version.h
> +++ b/libavcodec/version.h
> @@ -29,7 +29,7 @@
>
>  #include "version_major.h"
>
> -#define LIBAVCODEC_VERSION_MINOR  57
> +#define LIBAVCODEC_VERSION_MINOR  58
>  #define LIBAVCODEC_VERSION_MICRO 100
>
>  #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
> --
> 2.35.1
>
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