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avutil/gain_map: move ISO 21496-1 gain map payload parsing from libavcodec

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And export both functions. This is needed for a following change that will make
use of these functions from lavf.

Signed-off-by: James Almer <jamrial@gmail.com>
This commit is contained in:
James Almer committed 2026-10-12 10:39:10 -03:00
1 parent 409351e5eb
commit 2ac7367f2f
7 files changed
+177 -175
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doc/APIchanges
+4
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@@ -2,6 +2,10 @@ The last version increases of all libraries were on 2026-06-23.
API changes, most recent first:
2026-10-xx - xxxxxxxxxx - lavu 61.14.100 - gain_map.h
Add av_gain_map_params_from_iso21496() and av_gain_map_params_to_iso21496().
Add AV_GAIN_MAP_MAX_PAYLOAD_SIZE.
2026-10-12 - xxxxxxxxxx - lavc 63.19.100 - packet.h
Add AV_PKT_DATA_GAIN_MAP_PARAMS.
libavcodec/gain_map.c
-142
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@@ -28,148 +28,6 @@
#include "bytestream.h"
#include "gain_map.h"
#define ISO21496_HEADER_SIZE 5
#define ISO21496_FLAG_MULTICHANNEL (1 << 7)
#define ISO21496_FLAG_USE_BASE_CG (1 << 6)
#define ISO21496_FLAG_RESERVED 0x3f
static size_t iso21496_payload_size(int nb_channels)
{
return 4 * 4 + (size_t) nb_channels * 10 * 4;
}
static int make_q(int64_t num, uint32_t den, AVRational *out)
{
if (!den)
return AVERROR_INVALIDDATA;
/* Ensure the result fits in AVRational */
av_reduce(&out->num, &out->den, num, den, INT32_MAX);
return 0;
}
static int get_sq(GetByteContext *gb, AVRational *out)
{
int32_t num = (int32_t) bytestream2_get_be32(gb);
uint32_t den = bytestream2_get_be32u(gb);
return make_q(num, den, out);
}
static int get_uq(GetByteContext *gb, AVRational *out)
{
uint32_t num = bytestream2_get_be32u(gb);
uint32_t den = bytestream2_get_be32u(gb);
return make_q(num, den, out);
}
int ff_gain_map_params_from_iso21496(AVGainMapParams *restrict p,
const uint8_t *data, size_t size)
{
int ret;
if (!p || !data)
return AVERROR(EINVAL);
if (size < ISO21496_HEADER_SIZE || size > INT_MAX)
return AVERROR_INVALIDDATA;
GetByteContext gb;
bytestream2_init(&gb, data, size);
/* Parse header */
const uint16_t minimum_version = bytestream2_get_be16(&gb);
const uint16_t writer_version = bytestream2_get_be16(&gb);
if (minimum_version > FF_GAIN_MAP_VERSION || writer_version < minimum_version)
return AVERROR_PATCHWELCOME;
const uint8_t flags = bytestream2_get_byte(&gb);
/**
* While the spec does not require reserved bits to be 0, older versions
* of the ISO 21496-1 draft specification had extra flags that got removed
* from the final publication, so conservatively error out just in case;
* unless the writer version is >0 in which case these may be genuine
* additions to later revisions of the published spec, the validity of
* ignoring which is already guarded by the `minimum_version` check.
*/
if (writer_version == 0 && (flags & ISO21496_FLAG_RESERVED))
return AVERROR_INVALIDDATA;
p->version = FF_GAIN_MAP_VERSION;
p->nb_channels = (flags & ISO21496_FLAG_MULTICHANNEL) ? 3 : 1;
p->use_base_color_space = !!(flags & ISO21496_FLAG_USE_BASE_CG);
/* Parse payload */
if (bytestream2_get_bytes_left(&gb) < iso21496_payload_size(p->nb_channels))
return AVERROR_INVALIDDATA;
if ((ret = get_uq(&gb, &p->base_hdr_headroom)) < 0 ||
(ret = get_uq(&gb, &p->alternate_hdr_headroom)) < 0)
return ret;
for (int c = 0; c < p->nb_channels; c++) {
struct AVGainMapChannel *const ch = &p->channels[c];
if ((ret = get_sq(&gb, &ch->gain_map_min)) < 0 ||
(ret = get_sq(&gb, &ch->gain_map_max)) < 0 ||
(ret = get_uq(&gb, &ch->gamma)) < 0 ||
(ret = get_sq(&gb, &ch->base_offset)) < 0 ||
(ret = get_sq(&gb, &ch->alternate_offset)) < 0)
return ret;
}
/* nb_channels == 1 means every channel shares the same parameters */
for (int c = p->nb_channels; c < 3; c++)
p->channels[c] = p->channels[0];
return av_gain_map_params_validate(p);
}
static void put_q(PutByteContext *pb, AVRational q)
{
bytestream2_put_be32(pb, (unsigned) q.num);
bytestream2_put_be32(pb, (unsigned) q.den);
}
int ff_gain_map_params_to_iso21496(const AVGainMapParams *p, uint8_t *buf)
{
if (!p || !buf)
return AVERROR(EINVAL);
/* Ensures representability in the bitstream */
int ret = av_gain_map_params_validate(p);
if (ret < 0)
return ret;
if (p->version > FF_GAIN_MAP_VERSION)
return AVERROR_PATCHWELCOME; /* e.g. libraries out of sync */
PutByteContext pb;
bytestream2_init_writer(&pb, buf, FF_GAIN_MAP_MAX_PAYLOAD_SIZE);
int channels = av_gain_map_channels_identical(p) ? 1 : p->nb_channels;
uint8_t flags = 0;
if (channels == 3)
flags |= ISO21496_FLAG_MULTICHANNEL;
if (p->use_base_color_space)
flags |= ISO21496_FLAG_USE_BASE_CG;
bytestream2_put_be16(&pb, p->version); /* minimum_version */
bytestream2_put_be16(&pb, p->version); /* writer_version */
bytestream2_put_byte(&pb, flags);
put_q(&pb, p->base_hdr_headroom);
put_q(&pb, p->alternate_hdr_headroom);
for (int c = 0; c < channels; c++) {
const struct AVGainMapChannel *const ch = &p->channels[c];
put_q(&pb, ch->gain_map_min);
put_q(&pb, ch->gain_map_max);
put_q(&pb, ch->gamma);
put_q(&pb, ch->base_offset);
put_q(&pb, ch->alternate_offset);
}
return bytestream2_tell_p(&pb);
}
int ff_gain_map_params_check_xmp(const AVGainMapParams *p)
{
if (av_gain_map_params_validate(p) < 0)
libavcodec/gain_map.h
-30
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@@ -31,42 +31,12 @@
/* May differ from AV_ISO21496_VERSION if libraries are not in sync */
#define FF_GAIN_MAP_VERSION 0
#define FF_GAIN_MAP_MAX_PAYLOAD_SIZE 141 /* = 5 + 2*8 + 3*5*8 */
/* For XMP-based encoding */
#define FF_GAIN_MAP_XMP_IDENT "http://ns.adobe.com/xap/1.0/"
#define FF_GAIN_MAP_XMP_NAMESPACE "http://ns.adobe.com/hdr-gain-map/1.0/"
#define FF_GAIN_MAP_XMP_MAX_LEN 1024
/**
* Parse the payload of an ISO 21496-1 gain map metadata blob.
*
* @param p struct to fill; overwritten on success, untouched on failure
* @param data payload, excluding container-specific identifiers
* @param size size of `data` in bytes
*
* @return >= 0 on success, or a negative AVERROR on failure
*/
int ff_gain_map_params_from_iso21496(AVGainMapParams *p, const uint8_t *data,
size_t size);
/**
* Serialize an AVGainMapParams as an ISO 21496-1 gain map metadata blob.
*
* The output starts at the minimum_version field; the caller should prepend
* whatever identifier its container requires.
*
* @param p parameters to serialize
* @param buf Byte buffer to fill with the serialized data. Must contain at
* least FF_GAIN_MAP_MAX_PAYLOAD_SIZE bytes.
*
* @return Number of bytes written on success, or a negative AVERROR on failure
*
* @note Always succeeds if av_gain_map_params_validate() returns >= 0, and
* p->version <= AV_ISO21496_VERSION.
*/
int ff_gain_map_params_to_iso21496(const AVGainMapParams *p, uint8_t *buf);
/**
* Returns 1 if the gain map parameters are compatible with the XMP-based
* encoding, or 0 otherwise.
libavcodec/mjpegenc_common.c
+2 -2
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@@ -182,7 +182,7 @@ int ff_mjpeg_add_gain_map_size(AVCodecContext *avctx, struct MJpegContext *m,
if (ret < 0)
return ret;
size_t extra_size = 4 + sizeof(AV_ISO21496_IDENTIFIER) + FF_GAIN_MAP_MAX_PAYLOAD_SIZE;
size_t extra_size = 4 + sizeof(AV_ISO21496_IDENTIFIER) + AV_GAIN_MAP_MAX_PAYLOAD_SIZE;
if (m && m->xmp_gain_map) {
if (!ff_gain_map_params_check_xmp(params)) {
const int level = m->xmp_gain_map > 0 ? AV_LOG_ERROR : AV_LOG_WARNING;
@@ -294,7 +294,7 @@ static void jpeg_put_comments(AVCodecContext *avctx, PutBitContext *p,
flush_put_bits(p);
/* pre-validated by ff_mjpeg_add_gain_map_size() */
size = ff_gain_map_params_to_iso21496(gmp, put_bits_ptr(p));
size = av_gain_map_params_to_iso21496(gmp, put_bits_ptr(p));
av_assert0(size >= 0);
skip_put_bytes(p, size);
AV_WB16(ptr, 2 + sizeof(AV_ISO21496_IDENTIFIER) + size);
libavutil/gain_map.c
+140
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@@ -18,6 +18,7 @@
#include "gain_map.h"
#include "mem.h"
#include "libavcodec/bytestream.h"
static void gain_map_params_default(AVGainMapParams *p)
{
@@ -72,6 +73,145 @@ int av_gain_map_params_validate(const AVGainMapParams *p)
return 0;
}
#define ISO21496_HEADER_SIZE 5
#define ISO21496_FLAG_MULTICHANNEL (1 << 7)
#define ISO21496_FLAG_USE_BASE_CG (1 << 6)
#define ISO21496_FLAG_RESERVED 0x3f
static size_t iso21496_payload_size(int nb_channels)
{
return 4 * 4 + (size_t) nb_channels * 10 * 4;
}
static int make_q(int64_t num, uint32_t den, AVRational *out)
{
if (!den)
return AVERROR_INVALIDDATA;
/* Ensure the result fits in AVRational */
av_reduce(&out->num, &out->den, num, den, INT32_MAX);
return 0;
}
static int get_sq(GetByteContext *gb, AVRational *out)
{
int32_t num = (int32_t) bytestream2_get_be32(gb);
uint32_t den = bytestream2_get_be32u(gb);
return make_q(num, den, out);
}
static int get_uq(GetByteContext *gb, AVRational *out)
{
uint32_t num = bytestream2_get_be32u(gb);
uint32_t den = bytestream2_get_be32u(gb);
return make_q(num, den, out);
}
int av_gain_map_params_from_iso21496(AVGainMapParams *restrict p,
const uint8_t *data, size_t size)
{
int ret;
if (!p || !data)
return AVERROR(EINVAL);
if (size < ISO21496_HEADER_SIZE || size > INT_MAX)
return AVERROR_INVALIDDATA;
GetByteContext gb;
bytestream2_init(&gb, data, size);
/* Parse header */
const uint16_t minimum_version = bytestream2_get_be16(&gb);
const uint16_t writer_version = bytestream2_get_be16(&gb);
if (minimum_version > AV_ISO21496_VERSION || writer_version < minimum_version)
return AVERROR_PATCHWELCOME;
const uint8_t flags = bytestream2_get_byte(&gb);
/**
* While the spec does not require reserved bits to be 0, older versions
* of the ISO 21496-1 draft specification had extra flags that got removed
* from the final publication, so conservatively error out just in case;
* unless the writer version is >0 in which case these may be genuine
* additions to later revisions of the published spec, the validity of
* ignoring which is already guarded by the `minimum_version` check.
*/
if (writer_version == 0 && (flags & ISO21496_FLAG_RESERVED))
return AVERROR_INVALIDDATA;
p->version = AV_ISO21496_VERSION;
p->nb_channels = (flags & ISO21496_FLAG_MULTICHANNEL) ? 3 : 1;
p->use_base_color_space = !!(flags & ISO21496_FLAG_USE_BASE_CG);
/* Parse payload */
if (bytestream2_get_bytes_left(&gb) < iso21496_payload_size(p->nb_channels))
return AVERROR_INVALIDDATA;
if ((ret = get_uq(&gb, &p->base_hdr_headroom)) < 0 ||
(ret = get_uq(&gb, &p->alternate_hdr_headroom)) < 0)
return ret;
for (int c = 0; c < p->nb_channels; c++) {
struct AVGainMapChannel *const ch = &p->channels[c];
if ((ret = get_sq(&gb, &ch->gain_map_min)) < 0 ||
(ret = get_sq(&gb, &ch->gain_map_max)) < 0 ||
(ret = get_uq(&gb, &ch->gamma)) < 0 ||
(ret = get_sq(&gb, &ch->base_offset)) < 0 ||
(ret = get_sq(&gb, &ch->alternate_offset)) < 0)
return ret;
}
/* nb_channels == 1 means every channel shares the same parameters */
for (int c = p->nb_channels; c < 3; c++)
p->channels[c] = p->channels[0];
return av_gain_map_params_validate(p);
}
static void put_q(PutByteContext *pb, AVRational q)
{
bytestream2_put_be32(pb, (unsigned) q.num);
bytestream2_put_be32(pb, (unsigned) q.den);
}
int av_gain_map_params_to_iso21496(const AVGainMapParams *p, uint8_t *buf)
{
if (!p || !buf)
return AVERROR(EINVAL);
/* Ensures representability in the bitstream */
int ret = av_gain_map_params_validate(p);
if (ret < 0)
return ret;
PutByteContext pb;
bytestream2_init_writer(&pb, buf, AV_GAIN_MAP_MAX_PAYLOAD_SIZE);
int channels = av_gain_map_channels_identical(p) ? 1 : p->nb_channels;
uint8_t flags = 0;
if (channels == 3)
flags |= ISO21496_FLAG_MULTICHANNEL;
if (p->use_base_color_space)
flags |= ISO21496_FLAG_USE_BASE_CG;
bytestream2_put_be16(&pb, p->version); /* minimum_version */
bytestream2_put_be16(&pb, p->version); /* writer_version */
bytestream2_put_byte(&pb, flags);
put_q(&pb, p->base_hdr_headroom);
put_q(&pb, p->alternate_hdr_headroom);
for (int c = 0; c < channels; c++) {
const struct AVGainMapChannel *const ch = &p->channels[c];
put_q(&pb, ch->gain_map_min);
put_q(&pb, ch->gain_map_max);
put_q(&pb, ch->gamma);
put_q(&pb, ch->base_offset);
put_q(&pb, ch->alternate_offset);
}
return bytestream2_tell_p(&pb);
}
int av_gain_map_channels_identical(const AVGainMapParams *p)
{
static_assert(sizeof(p->channels[0]) == sizeof(int[2]) * 5,
libavutil/gain_map.h
+30
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@@ -83,6 +83,36 @@ typedef struct AVGainMapParams {
int nb_channels;
} AVGainMapParams;
/**
* Parse the payload of an ISO 21496-1 gain map metadata blob.
*
* @param p struct to fill; overwritten on success, untouched on failure
* @param data payload, excluding container-specific identifiers
* @param size size of `data` in bytes
*
* @return >= 0 on success, or a negative AVERROR on failure
*/
int av_gain_map_params_from_iso21496(AVGainMapParams *p, const uint8_t *data,
size_t size);
#define AV_GAIN_MAP_MAX_PAYLOAD_SIZE 141 /* = 5 + 2*8 + 3*5*8 */
/**
* Serialize an AVGainMapParams as an ISO 21496-1 gain map metadata blob.
*
* The output starts at the minimum_version field; the caller should prepend
* whatever identifier its container requires.
*
* @param p parameters to serialize
* @param buf Byte buffer to fill with the serialized data. Must contain at
* least AV_GAIN_MAP_MAX_PAYLOAD_SIZE bytes.
*
* @return Number of bytes written on success, or a negative AVERROR on failure
*
* @note Always succeeds if av_gain_map_params_validate() returns >= 0.
*/
int av_gain_map_params_to_iso21496(const AVGainMapParams *p, uint8_t *buf);
/**
* Returns >= 0 if the given AVGainMapParams struct contains valid data;
* or a negative AVERROR otherwise.
libavutil/version.h
+1 -1
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@@ -79,7 +79,7 @@
*/
#define LIBAVUTIL_VERSION_MAJOR 61
#define LIBAVUTIL_VERSION_MINOR 13
#define LIBAVUTIL_VERSION_MINOR 14
#define LIBAVUTIL_VERSION_MICRO 100
#define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \