[FFmpeg-devel] [PATCH 1/7] avutil: add an API to handle 3D Reference Displays Information
James Almer
jamrial at gmail.com
Sun Jun 8 18:45:29 EEST 2025
On 6/8/2025 11:29 AM, Andreas Rheinhardt wrote:
> Timo Rothenpieler:
>> From: James Almer <jamrial at gmail.com>
>>
>> As defined in section G.14.3.2.3 of ITU-T H.265, it's required for proper
>> signaling of MV-HEVC.
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>> libavutil/Makefile | 2 +
>> libavutil/tdrdi.c | 51 ++++++++++++++
>> libavutil/tdrdi.h | 164 +++++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 217 insertions(+)
>> create mode 100644 libavutil/tdrdi.c
>> create mode 100644 libavutil/tdrdi.h
>>
>> diff --git a/libavutil/Makefile b/libavutil/Makefile
>> index 9ef118016b..94a56bb72f 100644
>> --- a/libavutil/Makefile
>> +++ b/libavutil/Makefile
>> @@ -85,6 +85,7 @@ HEADERS = adler32.h \
>> sha512.h \
>> spherical.h \
>> stereo3d.h \
>> + tdrdi.h \
>> threadmessage.h \
>> time.h \
>> timecode.h \
>> @@ -179,6 +180,7 @@ OBJS = adler32.o \
>> slicethread.o \
>> spherical.o \
>> stereo3d.o \
>> + tdrdi.o \
>> threadmessage.o \
>> time.o \
>> timecode.o \
>> diff --git a/libavutil/tdrdi.c b/libavutil/tdrdi.c
>> new file mode 100644
>> index 0000000000..26192a1d2f
>> --- /dev/null
>> +++ b/libavutil/tdrdi.c
>> @@ -0,0 +1,51 @@
>> +/*
>> + * 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 <stddef.h>
>> +#include <stdint.h>
>> +
>> +#include "mem.h"
>> +#include "tdrdi.h"
>> +
>> +AV3DReferenceDisplaysInfo *av_tdrdi_alloc(unsigned int nb_displays, size_t *out_size)
>> +{
>> + struct TestStruct {
>> + AV3DReferenceDisplaysInfo p;
>> + AV3DReferenceDisplay b;
>> + };
>> + const size_t entries_offset = offsetof(struct TestStruct, b);
>> + size_t size = entries_offset;
>> + AV3DReferenceDisplaysInfo *tdrdi;
>> +
>> + if (nb_displays > (SIZE_MAX - size) / sizeof(AV3DReferenceDisplay))
>> + return NULL;
>> + size += sizeof(AV3DReferenceDisplay) * nb_displays;
>> +
>> + tdrdi = av_mallocz(size);
>> + if (!tdrdi)
>> + return NULL;
>> +
>> + tdrdi->num_ref_displays = nb_displays;
>> + tdrdi->entry_size = sizeof(AV3DReferenceDisplay);
>> + tdrdi->entries_offset = entries_offset;
>> +
>> + if (out_size)
>> + *out_size = size;
>> +
>> + return tdrdi;
>> +}
>> diff --git a/libavutil/tdrdi.h b/libavutil/tdrdi.h
>> new file mode 100644
>> index 0000000000..8dcca42c7b
>> --- /dev/null
>> +++ b/libavutil/tdrdi.h
>> @@ -0,0 +1,164 @@
>> +/*
>> + * 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
>> + * @ingroup lavu_video_3d_reference_displays_info
>> + * Spherical video
>> + */
>> +
>> +#ifndef AVUTIL_TDRDI_H
>> +#define AVUTIL_TDRDI_H
>> +
>> +#include <stddef.h>
>> +#include <stdint.h>
>> +
>> +#include "libavutil/avassert.h"
>> +
>> +/**
>> + * @defgroup lavu_video_3d_reference_displays_info 3D Reference Displays Information
>> + * @ingroup lavu_video
>> + *
>> + * The 3D Reference Displays Information describes information about the reference display
>> + * width(s) and reference viewing distance(s) as well as information about the corresponding
>> + * reference stereo pair(s).
>> + * @{
>> + */
>> +
>> +#define AV_TDRDI_MAX_NUM_REF_DISPLAY 32
>> +
>> +/**
>> + * This structure describes information about the reference display width(s) and reference
>> + * viewing distance(s) as well as information about the corresponding reference stereo pair(s).
>> + * See section G.14.3.2.3 of ITU-T H.265 for more information.
>> + *
>> + * @note The struct must be allocated with av_tdrdi_alloc() and
>> + * its size is not a part of the public ABI.
>> + */
>> +typedef struct AV3DReferenceDisplaysInfo {
>> + /**
>> + * The exponent of the maximum allowable truncation error for
>> + * {exponent,mantissa}_ref_display_width as given by 2<sup>(-prec_ref_display_width)</sup>.
>> + */
>> + uint8_t prec_ref_display_width;
>> +
>> + /**
>> + * A flag to indicate the presence of reference viewing distance.
>> + * If false, the values of prec_ref_viewing_dist, exponent_ref_viewing_distance,
>> + * and mantissa_ref_viewing_distance are undefined.
>> + */
>> + uint8_t ref_viewing_distance_flag;
>> +
>> + /**
>> + * The exponent of the maximum allowable truncation error for
>> + * {exponent,mantissa}_ref_viewing_distance as given by 2<sup>^(-prec_ref_viewing_dist)</sup>.
>> + * The value of prec_ref_viewing_dist shall be in the range of 0 to 31, inclusive.
>> + */
>> + uint8_t prec_ref_viewing_dist;
>> +
>> + /**
>> + * The number of reference displays that are signalled in this struct.
>> + * Allowed range is 1 to 32, inclusive.
>> + */
>> + uint8_t num_ref_displays;
>> +
>> + /**
>> + * Offset in bytes from the beginning of this structure at which the array
>> + * of reference displays starts.
>> + */
>> + size_t entries_offset;
>> +
>> + /**
>> + * Size of each entry in bytes. May not match sizeof(AV3DReferenceDisplay).
>> + */
>> + size_t entry_size;
>> +} AV3DReferenceDisplaysInfo;
>> +
>> +/**
>> + * Data structure for single deference display information.
>> + * It is allocated as a part of AV3DReferenceDisplaysInfo and should be retrieved with
>> + * av_tdrdi_get_display().
>> + *
>> + * sizeof(AV3DReferenceDisplay) is not a part of the ABI and new fields may be
>> + * added to it.
>> +*/
>> +typedef struct AV3DReferenceDisplay {
>> + /**
>> + * The ViewId of the left view of a stereo pair corresponding to the n-th reference display.
>> + */
>> + uint16_t left_view_id;
>> +
>> + /**
>> + * The ViewId of the left view of a stereo pair corresponding to the n-th reference display.
>> + */
>> + uint16_t right_view_id;
>> +
>> + /**
>> + * The exponent part of the reference display width of the n-th reference display.
>> + */
>> + uint8_t exponent_ref_display_width;
>> +
>> + /**
>> + * The mantissa part of the reference display width of the n-th reference display.
>> + */
>> + uint8_t mantissa_ref_display_width;
>> +
>> + /**
>> + * Tthe exponent part of the reference viewing distance of the n-th reference display.
>> + */
>> + uint8_t exponent_ref_viewing_distance;
>> +
>> + /**
>> + * The mantissa part of the reference viewing distance of the n-th reference display.
>> + */
>> + uint8_t mantissa_ref_viewing_distance;
>> +
>> + /**
>> + * An array of flags to indicates that the information about additional horizontal shift of
>> + * the left and right views for the n-th reference display is present.
>> + */
>> + uint8_t additional_shift_present_flag;
>> +
>> + /**
>> + * The recommended additional horizontal shift for a stereo pair corresponding to the n-th
>> + * reference baseline and the n-th reference display.
>> + */
>> + int16_t num_sample_shift;
>> +} AV3DReferenceDisplay;
>> +
>> +static av_always_inline AV3DReferenceDisplay*
>> +av_tdrdi_get_display(AV3DReferenceDisplaysInfo *tdrdi, unsigned int idx)
>> +{
>> + av_assert0(idx < tdrdi->num_ref_displays);
>> + return (AV3DReferenceDisplay *)((uint8_t *)tdrdi + tdrdi->entries_offset +
>> + idx * tdrdi->entry_size);
>> +}
>> +
>> +/**
>> + * Allocate a AV3DReferenceDisplaysInfo structure and initialize its fields to default
>> + * values.
>> + *
>> + * @return the newly allocated struct or NULL on failure
>> + */
>> +AV3DReferenceDisplaysInfo *av_tdrdi_alloc(unsigned int nb_displays, size_t *size);
>> +
>> +/**
>> + * @}
>> + */
>> +
>> +#endif /* AVUTIL_TDRDI_H */
>
> I don't like that you add another allocator for this; instead we should
> add a generic allocator for the frame side-data types.
Wont work for packet side data. And i purposely didn't add yet another
allocator that inserts the result into a frame, like there's in so many
other modules, because eventually the generic one would be introduced.
You said you wanted to take over my work on the generic allocator, but
not sure if you did anything with it. The core issue was handling more
complex types that didn't just have an extra nb_blocks argument.
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