FFmpeg/libavcodec/h264_redundant_pps_bsf.c
Andreas Rheinhardt 7ae1c0dd3e avcodec/h264_redundant_pps_bsf: Don't remove PPS
There is no check for whether these supposedly redundant PPS
are actually redundant. One could check via memcmp which would
work in practice* (because all content buffers are initially
zero-allocated), but this is not portable as compilers may
trash padding inside structures as they wish.

In case the PPS is not really redundant the output is garbage.
This happens with several files from the FATE-suite. E.g.
h264-conformance/CVCANLMA2_Sony_C.jsv doesn't decode correctly
any more, whereas h264-conformance/CABA3_TOSHIBA_E.264 even
fails in ff_cbs_write_packet(), because the inferred value
of num_ref_idx_l0_active_minus1 mismatches with the value set
in the slice (this happens when num_ref_idx_l0_default_active_minus1
changes in the PPS; the value in the slice header is inferred from
the original PPS's num_ref_idx_l0_default_active_minus1).

*: Unless slice_group_id is used, i.e. unless slice_group_map_type
is six.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2022-09-25 14:53:45 +02:00

127 lines
4.0 KiB
C

/*
* 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 <inttypes.h>
#include "libavutil/log.h"
#include "bsf.h"
#include "bsf_internal.h"
#include "cbs.h"
#include "cbs_bsf.h"
#include "cbs_h264.h"
#include "codec_id.h"
#include "h264.h"
#include "packet.h"
#define NEW_GLOBAL_PIC_INIT_QP 26
typedef struct H264RedundantPPSContext {
CBSBSFContext common;
} H264RedundantPPSContext;
static int h264_redundant_pps_fixup_pps(H264RedundantPPSContext *ctx,
CodedBitstreamUnit *unit)
{
H264RawPPS *pps;
int err;
// The changes we are about to perform affect the parsing process,
// so we must make sure that the PPS is writable, otherwise the
// parsing of future slices will be incorrect and even raise errors.
err = ff_cbs_make_unit_writable(ctx->common.input, unit);
if (err < 0)
return err;
pps = unit->content;
// Overwrite pic_init_qp with the global value.
pps->pic_init_qp_minus26 = NEW_GLOBAL_PIC_INIT_QP - 26;
// Some PPSs have this set, so it must be set in all of them.
// (Slices which do not use such a PPS on input will still have
// *_weight_l*flag as zero and therefore write equivalently.)
pps->weighted_pred_flag = 1;
return 0;
}
static int h264_redundant_pps_fixup_slice(H264RedundantPPSContext *ctx,
H264RawSliceHeader *slice)
{
const CodedBitstreamH264Context *const in = ctx->common.input->priv_data;
const H264RawPPS *const pps = in->pps[slice->pic_parameter_set_id];
// We modified the PPS's qp value, now offset this by applying
// the negative offset to the slices.
slice->slice_qp_delta += pps->pic_init_qp_minus26
- (NEW_GLOBAL_PIC_INIT_QP - 26);
return 0;
}
static int h264_redundant_pps_update_fragment(AVBSFContext *bsf,
AVPacket *pkt,
CodedBitstreamFragment *au)
{
H264RedundantPPSContext *ctx = bsf->priv_data;
int err, i;
for (i = 0; i < au->nb_units; i++) {
CodedBitstreamUnit *nal = &au->units[i];
if (nal->type == H264_NAL_PPS) {
err = h264_redundant_pps_fixup_pps(ctx, nal);
if (err < 0)
return err;
}
if (nal->type == H264_NAL_SLICE ||
nal->type == H264_NAL_IDR_SLICE) {
H264RawSlice *slice = nal->content;
h264_redundant_pps_fixup_slice(ctx, &slice->header);
}
}
return 0;
}
static const CBSBSFType h264_redundant_pps_type = {
.codec_id = AV_CODEC_ID_H264,
.fragment_name = "access unit",
.unit_name = "NAL unit",
.update_fragment = &h264_redundant_pps_update_fragment,
};
static int h264_redundant_pps_init(AVBSFContext *bsf)
{
return ff_cbs_bsf_generic_init(bsf, &h264_redundant_pps_type);
}
static const enum AVCodecID h264_redundant_pps_codec_ids[] = {
AV_CODEC_ID_H264, AV_CODEC_ID_NONE,
};
const FFBitStreamFilter ff_h264_redundant_pps_bsf = {
.p.name = "h264_redundant_pps",
.p.codec_ids = h264_redundant_pps_codec_ids,
.priv_data_size = sizeof(H264RedundantPPSContext),
.init = &h264_redundant_pps_init,
.close = &ff_cbs_bsf_generic_close,
.filter = &ff_cbs_bsf_generic_filter,
};