[FFmpeg-devel,v14,2/4] avcodec/libjxl: add Jpeg XL decoding via libjxl

This commit adds decoding support to libavcodec
for Jpeg XL images via the external library libjxl.
---
 MAINTAINERS               |   1 +
 configure                 |   5 +
 doc/general_contents.texi |   7 +
 libavcodec/Makefile       |   1 +
 libavcodec/allcodecs.c    |   1 +
 libavcodec/libjxl.c       |  70 ++++++++++
 libavcodec/libjxl.h       |  48 +++++++
 libavcodec/libjxldec.c    | 274 ++++++++++++++++++++++++++++++++++++++
 8 files changed, 407 insertions(+)
 create mode 100644 libavcodec/libjxl.c
 create mode 100644 libavcodec/libjxl.h
 create mode 100644 libavcodec/libjxldec.c

Leo Izen:
> This commit adds decoding support to libavcodec
> for Jpeg XL images via the external library libjxl.
> ---
>  MAINTAINERS               |   1 +
>  configure                 |   5 +
>  doc/general_contents.texi |   7 +
>  libavcodec/Makefile       |   1 +
>  libavcodec/allcodecs.c    |   1 +
>  libavcodec/libjxl.c       |  70 ++++++++++
>  libavcodec/libjxl.h       |  48 +++++++
>  libavcodec/libjxldec.c    | 274 ++++++++++++++++++++++++++++++++++++++
>  8 files changed, 407 insertions(+)
>  create mode 100644 libavcodec/libjxl.c
>  create mode 100644 libavcodec/libjxl.h
>  create mode 100644 libavcodec/libjxldec.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 859a5005d4..faea84ebf1 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -194,6 +194,7 @@ Codecs:
>    libcodec2.c                           Tomas Härdin
>    libdirac*                             David Conrad
>    libdavs2.c                            Huiwen Ren
> +  libjxl*.c, libjxl.h                   Leo Izen
>    libgsm.c                              Michel Bardiaux
>    libkvazaar.c                          Arttu Ylä-Outinen
>    libopenh264enc.c                      Martin Storsjo, Linjie Fu
> diff --git a/configure b/configure
> index 9c8965852b..c36d5dbc8b 100755
> --- a/configure
> +++ b/configure
> @@ -240,6 +240,7 @@ External library support:
>    --enable-libiec61883     enable iec61883 via libiec61883 [no]
>    --enable-libilbc         enable iLBC de/encoding via libilbc [no]
>    --enable-libjack         enable JACK audio sound server [no]
> +  --enable-libjxl          enable JPEG XL decoding via libjxl [no]
>    --enable-libklvanc       enable Kernel Labs VANC processing [no]
>    --enable-libkvazaar      enable HEVC encoding via libkvazaar [no]
>    --enable-liblensfun      enable lensfun lens correction [no]
> @@ -1833,6 +1834,7 @@ EXTERNAL_LIBRARY_LIST="
>      libiec61883
>      libilbc
>      libjack
> +    libjxl
>      libklvanc
>      libkvazaar
>      libmodplug
> @@ -3331,6 +3333,7 @@ libgsm_ms_decoder_deps="libgsm"
>  libgsm_ms_encoder_deps="libgsm"
>  libilbc_decoder_deps="libilbc"
>  libilbc_encoder_deps="libilbc"
> +libjxl_decoder_deps="libjxl libjxl_threads"
>  libkvazaar_encoder_deps="libkvazaar"
>  libmodplug_demuxer_deps="libmodplug"
>  libmp3lame_encoder_deps="libmp3lame"
> @@ -6543,6 +6546,8 @@ enabled libgsm            && { for gsm_hdr in "gsm.h" "gsm/gsm.h"; do
>                                     check_lib libgsm "${gsm_hdr}" gsm_create -lgsm && break;
>                                 done || die "ERROR: libgsm not found"; }
>  enabled libilbc           && require libilbc ilbc.h WebRtcIlbcfix_InitDecode -lilbc $pthreads_extralibs
> +enabled libjxl            && require_pkg_config libjxl "libjxl >= 0.7.0" jxl/decode.h JxlDecoderVersion &&
> +                             require_pkg_config libjxl_threads "libjxl_threads >= 0.7.0" jxl/thread_parallel_runner.h JxlThreadParallelRunner
>  enabled libklvanc         && require libklvanc libklvanc/vanc.h klvanc_context_create -lklvanc
>  enabled libkvazaar        && require_pkg_config libkvazaar "kvazaar >= 0.8.1" kvazaar.h kvz_api_get
>  enabled liblensfun        && require_pkg_config liblensfun lensfun lensfun.h lf_db_new
> diff --git a/doc/general_contents.texi b/doc/general_contents.texi
> index 238568f2bb..93a90a5e52 100644
> --- a/doc/general_contents.texi
> +++ b/doc/general_contents.texi
> @@ -171,6 +171,13 @@ Go to @url{https://github.com/TimothyGu/libilbc} and follow the instructions for
>  installing the library. Then pass @code{--enable-libilbc} to configure to
>  enable it.
>  
> +@section libjxl
> +
> +JPEG XL is an image format intended to fully replace legacy JPEG for an extended
> +period of life. See @url{https://jpegxl.info/} for more information, and see
> +@url{https://github.com/libjxl/libjxl} for the library source. You can pass
> +@code{--enable-libjxl} to configure in order enable the libjxl wrapper.
> +
>  @section libvpx
>  
>  FFmpeg can make use of the libvpx library for VP8/VP9 decoding and encoding.
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index 90f46035d9..8fc3b3cc5f 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -1061,6 +1061,7 @@ OBJS-$(CONFIG_LIBGSM_MS_DECODER)          += libgsmdec.o
>  OBJS-$(CONFIG_LIBGSM_MS_ENCODER)          += libgsmenc.o
>  OBJS-$(CONFIG_LIBILBC_DECODER)            += libilbc.o
>  OBJS-$(CONFIG_LIBILBC_ENCODER)            += libilbc.o
> +OBJS-$(CONFIG_LIBJXL_DECODER)             += libjxldec.o libjxl.o
>  OBJS-$(CONFIG_LIBKVAZAAR_ENCODER)         += libkvazaar.o
>  OBJS-$(CONFIG_LIBMP3LAME_ENCODER)         += libmp3lame.o
>  OBJS-$(CONFIG_LIBOPENCORE_AMRNB_DECODER)  += libopencore-amr.o
> diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
> index 585918da93..07f5bafd27 100644
> --- a/libavcodec/allcodecs.c
> +++ b/libavcodec/allcodecs.c
> @@ -751,6 +751,7 @@ extern const FFCodec ff_libgsm_ms_encoder;
>  extern const FFCodec ff_libgsm_ms_decoder;
>  extern const FFCodec ff_libilbc_encoder;
>  extern const FFCodec ff_libilbc_decoder;
> +extern const FFCodec ff_libjxl_decoder;
>  extern const FFCodec ff_libmp3lame_encoder;
>  extern const FFCodec ff_libopencore_amrnb_encoder;
>  extern const FFCodec ff_libopencore_amrnb_decoder;
> diff --git a/libavcodec/libjxl.c b/libavcodec/libjxl.c
> new file mode 100644
> index 0000000000..204d91d8a8
> --- /dev/null
> +++ b/libavcodec/libjxl.c
> @@ -0,0 +1,70 @@
> +/*
> + * JPEG XL de/encoding via libjxl, common support implementation
> + * Copyright (c) 2021 Leo Izen <leo.izen@gmail.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
> + */
> +
> +/**
> + * @file
> + * JPEG XL via libjxl common support implementation
> + */
> +
> +#include "libavutil/cpu.h"
> +#include "libavutil/mem.h"
> +
> +#include <jxl/memory_manager.h>
> +#include "libjxl.h"
> +
> +size_t ff_libjxl_get_threadcount(int threads)
> +{
> +    if (threads <= 0)
> +        return av_cpu_count();
> +    if (threads == 1)
> +        return 0;
> +    return threads;
> +}
> +
> +/**
> + * Wrapper around av_malloc used as a jpegxl_alloc_func.
> + *
> + * @param  opaque opaque pointer for jpegxl_alloc_func, always ignored
> + * @param  size Size in bytes for the memory block to be allocated
> + * @return Pointer to the allocated block, or `NULL` if it cannot be allocated
> + */
> +static void *libjxl_av_malloc(void *opaque, size_t size)
> +{
> +    return av_malloc(size);
> +}
> +
> +/**
> + * Wrapper around av_free used as a jpegxl_free_func.
> + *
> + * @param opaque  opaque pointer for jpegxl_free_func, always ignored
> + * @param address Pointer to the allocated block, to free. `NULL` permitted as a no-op.
> + */
> +static void libjxl_av_free(void *opaque, void *address)
> +{
> +    av_free(address);
> +}
> +
> +void ff_libjxl_init_memory_manager(JxlMemoryManager *manager)
> +{
> +    manager->opaque = NULL;
> +    manager->alloc = &libjxl_av_malloc;
> +    manager->free = &libjxl_av_free;
> +}
> diff --git a/libavcodec/libjxl.h b/libavcodec/libjxl.h
> new file mode 100644
> index 0000000000..5387c438fd
> --- /dev/null
> +++ b/libavcodec/libjxl.h
> @@ -0,0 +1,48 @@
> +/*
> + * JPEG XL de/encoding via libjxl, common support header
> + * Copyright (c) 2021 Leo Izen <leo.izen@gmail.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
> + */
> +
> +/**
> + * @file
> + * JPEG XL via libjxl common support header
> + */
> +
> +#ifndef AVCODEC_LIBJXL_H
> +#define AVCODEC_LIBJXL_H
> +
> +#include <jxl/memory_manager.h>
> +
> +/**
> + * Transform threadcount in ffmpeg to one used by libjxl.
> + *
> + * @param  threads ffmpeg's threads AVOption
> + * @return         thread count for libjxl's parallel runner
> + */
> +size_t ff_libjxl_get_threadcount(int threads);
> +
> +/**
> + * Initialize and populate a JxlMemoryManager
> + * with av_malloc() and av_free() so libjxl will use these
> + * functions.
> + * @param manager a pointer to a JxlMemoryManager struct
> + */
> +void ff_libjxl_init_memory_manager(JxlMemoryManager *manager);
> +
> +#endif /* AVCODEC_LIBJXL_H */
> diff --git a/libavcodec/libjxldec.c b/libavcodec/libjxldec.c
> new file mode 100644
> index 0000000000..a7d205b081
> --- /dev/null
> +++ b/libavcodec/libjxldec.c
> @@ -0,0 +1,274 @@
> +/*
> + * JPEG XL decoding support via libjxl
> + * Copyright (c) 2021 Leo Izen <leo.izen@gmail.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
> + */
> +
> +/**
> + * @file
> + * JPEG XL decoder using libjxl
> + */
> +
> +#include "libavutil/avassert.h"
> +#include "libavutil/buffer.h"
> +#include "libavutil/common.h"
> +#include "libavutil/error.h"
> +#include "libavutil/mem.h"
> +#include "libavutil/pixdesc.h"
> +#include "libavutil/pixfmt.h"
> +#include "libavutil/frame.h"
> +
> +#include "avcodec.h"
> +#include "codec_internal.h"
> +#include "internal.h"
> +
> +#include <jxl/decode.h>
> +#include <jxl/thread_parallel_runner.h>
> +#include "libjxl.h"
> +
> +typedef struct LibJxlDecodeContext {
> +    void *runner;
> +    JxlDecoder *decoder;
> +    JxlBasicInfo basic_info;
> +    JxlPixelFormat jxl_pixfmt;
> +    JxlDecoderStatus events;
> +    AVBufferRef *iccp;
> +} LibJxlDecodeContext;
> +
> +static int libjxl_init_jxl_decoder(AVCodecContext *avctx)
> +{
> +    LibJxlDecodeContext *ctx = avctx->priv_data;
> +
> +    ctx->events = JXL_DEC_BASIC_INFO | JXL_DEC_FULL_IMAGE | JXL_DEC_COLOR_ENCODING;
> +    if (JxlDecoderSubscribeEvents(ctx->decoder, ctx->events) != JXL_DEC_SUCCESS) {
> +        av_log(avctx, AV_LOG_ERROR, "Error subscribing to JXL events\n");
> +        return AVERROR_EXTERNAL;
> +    }
> +
> +    if (JxlDecoderSetParallelRunner(ctx->decoder, JxlThreadParallelRunner, ctx->runner) != JXL_DEC_SUCCESS) {
> +        av_log(avctx, AV_LOG_ERROR, "Failed to set JxlThreadParallelRunner\n");
> +        return AVERROR_EXTERNAL;
> +    }
> +
> +    memset(&ctx->basic_info, 0, sizeof(JxlBasicInfo));
> +    memset(&ctx->jxl_pixfmt, 0, sizeof(JxlPixelFormat));
> +
> +    return 0;
> +}
> +
> +static av_cold int libjxl_decode_init(AVCodecContext *avctx)
> +{
> +    LibJxlDecodeContext *ctx = avctx->priv_data;
> +    JxlMemoryManager manager;
> +
> +    ff_libjxl_init_memory_manager(&manager);
> +    ctx->decoder = JxlDecoderCreate(&manager);
> +    if (!ctx->decoder) {
> +        av_log(avctx, AV_LOG_ERROR, "Failed to create JxlDecoder\n");
> +        return AVERROR_EXTERNAL;
> +    }
> +
> +    ctx->runner = JxlThreadParallelRunnerCreate(&manager, ff_libjxl_get_threadcount(avctx->thread_count));
> +    if (!ctx->runner) {
> +        av_log(avctx, AV_LOG_ERROR, "Failed to create JxlThreadParallelRunner\n");
> +        return AVERROR_EXTERNAL;
> +    }
> +
> +    return libjxl_init_jxl_decoder(avctx);
> +}
> +
> +static enum AVPixelFormat libjxl_get_pix_fmt(AVCodecContext *avctx, JxlBasicInfo *basic_info, JxlPixelFormat *format)
> +{
> +    format->endianness = JXL_NATIVE_ENDIAN;
> +    format->num_channels = basic_info->num_color_channels + (basic_info->alpha_bits > 0);
> +    /* Gray */
> +    if (basic_info->num_color_channels == 1) {
> +        if (basic_info->bits_per_sample <= 8) {
> +            format->data_type = JXL_TYPE_UINT8;
> +            return basic_info->alpha_bits ? AV_PIX_FMT_YA8 : AV_PIX_FMT_GRAY8;
> +        }
> +        if (basic_info->exponent_bits_per_sample || basic_info->bits_per_sample > 16) {
> +            if (basic_info->alpha_bits)
> +                return AV_PIX_FMT_NONE;
> +            format->data_type = JXL_TYPE_FLOAT;
> +            return AV_PIX_FMT_GRAYF32;
> +        }
> +        format->data_type = JXL_TYPE_UINT16;
> +        return basic_info->alpha_bits ? AV_PIX_FMT_YA16 : AV_PIX_FMT_GRAY16;
> +    }
> +    /* rgb only */
> +    /* libjxl only supports packed RGB and gray output at the moment */
> +    if (basic_info->num_color_channels == 3) {
> +        if (basic_info->bits_per_sample <= 8) {
> +            format->data_type = JXL_TYPE_UINT8;
> +            return basic_info->alpha_bits ? AV_PIX_FMT_RGBA : AV_PIX_FMT_RGB24;
> +        }
> +        if (basic_info->bits_per_sample > 16)
> +            av_log(avctx, AV_LOG_WARNING, "Downsampling larger integer to 16-bit via libjxl\n");
> +        if (basic_info->exponent_bits_per_sample)
> +            av_log(avctx, AV_LOG_WARNING, "Downsampling float to 16-bit integer via libjxl\n");
> +        format->data_type = JXL_TYPE_UINT16;
> +        return basic_info->alpha_bits ? AV_PIX_FMT_RGBA64 : AV_PIX_FMT_RGB48;
> +    }
> +
> +    return AV_PIX_FMT_NONE;
> +}
> +
> +static int libjxl_decode_frame(AVCodecContext *avctx, AVFrame *frame, int *got_frame, AVPacket *avpkt)
> +{
> +    LibJxlDecodeContext *ctx = avctx->priv_data;
> +    uint8_t *buf = avpkt->data;
> +    size_t remaining = avpkt->size, iccp_len;
> +    JxlDecoderStatus jret;
> +    int ret;
> +    *got_frame = 0;
> +
> +    while (1) {
> +
> +        jret = JxlDecoderSetInput(ctx->decoder, buf, remaining);
> +
> +        if (jret == JXL_DEC_ERROR) {
> +            /* this should never happen here unless there's a bug in libjxl */
> +            av_log(avctx, AV_LOG_ERROR, "Unknown libjxl decode error\n");
> +            return AVERROR_EXTERNAL;
> +        }
> +
> +        jret = JxlDecoderProcessInput(ctx->decoder);
> +        /*
> +         * JxlDecoderReleaseInput returns the number
> +         * of bytes remaining to be read, rather than
> +         * the number of bytes that it did read
> +         */
> +        remaining = JxlDecoderReleaseInput(ctx->decoder);
> +        buf = avpkt->data + avpkt->size - remaining;
> +
> +        switch(jret) {
> +        case JXL_DEC_ERROR:
> +            av_log(avctx, AV_LOG_ERROR, "Unknown libjxl decode error\n");
> +            return AVERROR_INVALIDDATA;
> +        case JXL_DEC_NEED_MORE_INPUT:
> +            if (remaining == 0) {
> +                av_log(avctx, AV_LOG_ERROR, "Unexpected end of JXL codestream\n");
> +                return AVERROR_INVALIDDATA;
> +            }
> +            av_log(avctx, AV_LOG_DEBUG, "NEED_MORE_INPUT event emitted\n");
> +            continue;
> +        case JXL_DEC_BASIC_INFO:
> +            av_log(avctx, AV_LOG_DEBUG, "BASIC_INFO event emitted\n");
> +            if (JxlDecoderGetBasicInfo(ctx->decoder, &ctx->basic_info) != JXL_DEC_SUCCESS) {
> +                /*
> +                 * this should never happen
> +                 * if it does it is likely a libjxl decoder bug
> +                 */
> +                av_log(avctx, AV_LOG_ERROR, "Bad libjxl basic info event\n");
> +                return AVERROR_EXTERNAL;
> +            }
> +            avctx->pix_fmt = libjxl_get_pix_fmt(avctx, &ctx->basic_info, &ctx->jxl_pixfmt);
> +            if (avctx->pix_fmt == AV_PIX_FMT_NONE) {
> +                av_log(avctx, AV_LOG_ERROR, "Bad libjxl pixel format\n");
> +                return AVERROR_EXTERNAL;
> +            }
> +            ret = ff_set_dimensions(avctx, ctx->basic_info.xsize, ctx->basic_info.ysize);
> +            if (ret < 0)
> +                return ret;
> +            continue;
> +        case JXL_DEC_COLOR_ENCODING:
> +            av_log(avctx, AV_LOG_DEBUG, "COLOR_ENCODING event emitted\n");
> +            jret = JxlDecoderGetICCProfileSize(ctx->decoder, &ctx->jxl_pixfmt, JXL_COLOR_PROFILE_TARGET_ORIGINAL, &iccp_len);
> +            if (jret == JXL_DEC_SUCCESS && iccp_len > 0) {
> +                av_buffer_unref(&ctx->iccp);
> +                ctx->iccp = av_buffer_alloc(iccp_len);
> +                if (!ctx->iccp)
> +                    return AVERROR(ENOMEM);
> +                jret = JxlDecoderGetColorAsICCProfile(ctx->decoder, &ctx->jxl_pixfmt, JXL_COLOR_PROFILE_TARGET_ORIGINAL, ctx->iccp->data, iccp_len);
> +                if (jret != JXL_DEC_SUCCESS)
> +                    av_buffer_unref(&ctx->iccp);
> +            }
> +            continue;
> +        case JXL_DEC_NEED_IMAGE_OUT_BUFFER:
> +            av_log(avctx, AV_LOG_DEBUG, "NEED_IMAGE_OUT_BUFFER event emitted\n");
> +            ret = ff_get_buffer(avctx, frame, 0);
> +            if (ret < 0)
> +                return ret;
> +            ctx->jxl_pixfmt.align = frame->linesize[0];
> +            if (JxlDecoderSetImageOutBuffer(ctx->decoder, &ctx->jxl_pixfmt, frame->data[0], frame->buf[0]->size) != JXL_DEC_SUCCESS) {
> +                av_log(avctx, AV_LOG_ERROR, "Bad libjxl dec need image out buffer event\n");
> +                return AVERROR_EXTERNAL;
> +            }
> +            continue;
> +        case JXL_DEC_FULL_IMAGE:
> +            /* full image is one frame, even if animated */
> +            av_log(avctx, AV_LOG_DEBUG, "FULL_IMAGE event emitted\n");
> +            *got_frame = 1;

Only set this after you know that you return successfully (i.e. after
the av_frame_new_side_data_from_buf()).

> +            frame->pict_type = AV_PICTURE_TYPE_I;
> +            frame->key_frame = 1;
> +            if (ctx->iccp) {
> +                AVFrameSideData *sd = av_frame_new_side_data_from_buf(frame, AV_FRAME_DATA_ICC_PROFILE, ctx->iccp);
> +                if (!sd)
> +                    return AVERROR(ENOMEM);
> +                /* ownership is transfered, and it is not ref-ed */
> +                ctx->iccp = NULL;
> +            }
> +            return avpkt->size - remaining;

If this decoder is supposed to produce multiple frames from one packet
of input, it needs to use the receive_frame-callback. For video
decoders, it is only checked whether the return value is >= 0 or not
(see lines 451-456 in decode.c).

> +        case JXL_DEC_SUCCESS:
> +            av_log(avctx, AV_LOG_DEBUG, "SUCCESS event emitted\n");
> +            /*
> +             * The file has finished decoding
> +             * reset the decoder to let us
> +             * reuse it again for the next image
> +             */
> +            JxlDecoderReset(ctx->decoder);
> +            libjxl_init_jxl_decoder(avctx);

You are only resetting the decoder on success. What happens if any of
the errors happened? Would the decoder need to be reset before decoding
the next picture?

> +            buf = avpkt->data;
> +            remaining = avpkt->size;
> +            continue;

Didn't you already feed this data to the decoder? This somehow looks
like a recipe for an infinite loop.

> +        default:
> +             av_log(avctx, AV_LOG_ERROR, "Bad libjxl event: %d\n", jret);
> +             return AVERROR_EXTERNAL;
> +        }
> +    }
> +}
> +
> +static av_cold int libjxl_decode_close(AVCodecContext *avctx)
> +{
> +    LibJxlDecodeContext *ctx = avctx->priv_data;
> +
> +    if (ctx->runner)
> +        JxlThreadParallelRunnerDestroy(ctx->runner);
> +    ctx->runner = NULL;
> +    if (ctx->decoder)
> +        JxlDecoderDestroy(ctx->decoder);
> +    ctx->decoder = NULL;
> +    av_buffer_unref(&ctx->iccp);
> +
> +    return 0;
> +}
> +
> +const FFCodec ff_libjxl_decoder = {
> +    .p.name           = "libjxl",
> +    .p.long_name      = NULL_IF_CONFIG_SMALL("libjxl JPEG XL"),
> +    .p.type           = AVMEDIA_TYPE_VIDEO,
> +    .p.id             = AV_CODEC_ID_JPEGXL,
> +    .priv_data_size   = sizeof(LibJxlDecodeContext),
> +    .init             = libjxl_decode_init,
> +    FF_CODEC_DECODE_CB(libjxl_decode_frame),
> +    .close            = libjxl_decode_close,
> +    .p.capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_OTHER_THREADS,
> +    .caps_internal    = FF_CODEC_CAP_AUTO_THREADS | FF_CODEC_CAP_INIT_CLEANUP,
> +    .p.wrapper_name   = "libjxl",
> +};

- Andreas

PS: I apologize in advance if any of the above points has already been
raised and shown to be non-issues.

On 4/15/22 07:08, Andreas Rheinhardt wrote:
> Leo Izen:
>
>> +            return avpkt->size - remaining;
> If this decoder is supposed to produce multiple frames from one packet
> of input, it needs to use the receive_frame-callback. For video
> decoders, it is only checked whether the return value is >= 0 or not
> (see lines 451-456 in decode.c).
It isn't, because I've chosen not to support animated JXL at this time. 
As far as I'm aware an animated JXL file will just decode to its first 
frame with this decoder.
>> +        case JXL_DEC_SUCCESS:
>> +            av_log(avctx, AV_LOG_DEBUG, "SUCCESS event emitted\n");
>> +            /*
>> +             * The file has finished decoding
>> +             * reset the decoder to let us
>> +             * reuse it again for the next image
>> +             */
>> +            JxlDecoderReset(ctx->decoder);
>> +            libjxl_init_jxl_decoder(avctx);
> You are only resetting the decoder on success. What happens if any of
> the errors happened? Would the decoder need to be reset before decoding
> the next picture?
This was already brought up by Anton. The JXL_DEC_SUCCESS event isn't 
fired until the start of the next packet (if there is one). It is the 
"finished decoding" event which we never actually get to for single 
images because JXL_DEC_FULL_IMAGE is always fired first. If this is 
fired it means we're in an image2 sequence and this is the next frame, 
at which point the data will have been swapped out. Resetting the 
decoder is necessary here to make the library re-read the header info 
and not whine. I agree that it's a bit confusing and I should probably 
add a block comment explaining this.
>> +            buf = avpkt->data;
>> +            remaining = avpkt->size;
>> +            continue;
> Didn't you already feed this data to the decoder? This somehow looks
> like a recipe for an infinite loop.
No, see up.

- Leo Izen (thebombzen)