FFmpeg/libavcodec/h264_redundant_pps_bsf.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 <string.h>

#include "libavutil/common.h"
#include "libavutil/mem.h"

#include "bsf.h"
#include "bsf_internal.h"
#include "cbs.h"
#include "cbs_h264.h"
#include "h264.h"


typedef struct H264RedundantPPSContext {
    CodedBitstreamContext *input;
    CodedBitstreamContext *output;

    CodedBitstreamFragment access_unit;

    int global_pic_init_qp;
    int current_pic_init_qp;
    int extradata_pic_init_qp;
} 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->input, unit);
    if (err < 0)
        return err;
    pps = unit->content;

    // Record the current value of pic_init_qp in order to fix up
    // following slices, then overwrite with the global value.
    ctx->current_pic_init_qp = pps->pic_init_qp_minus26 + 26;
    pps->pic_init_qp_minus26 = ctx->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)
{
    int qp;

    qp = ctx->current_pic_init_qp + slice->slice_qp_delta;
    slice->slice_qp_delta = qp - ctx->global_pic_init_qp;

    return 0;
}

static int h264_redundant_pps_filter(AVBSFContext *bsf, AVPacket *pkt)
{
    H264RedundantPPSContext *ctx = bsf->priv_data;
    CodedBitstreamFragment *au = &ctx->access_unit;
    int au_has_sps;
    int err, i;

    err = ff_bsf_get_packet_ref(bsf, pkt);
    if (err < 0)
        return err;

    err = ff_cbs_read_packet(ctx->input, au, pkt);
    if (err < 0)
        goto fail;

    au_has_sps = 0;
    for (i = 0; i < au->nb_units; i++) {
        CodedBitstreamUnit *nal = &au->units[i];

        if (nal->type == H264_NAL_SPS)
            au_has_sps = 1;
        if (nal->type == H264_NAL_PPS) {
            err = h264_redundant_pps_fixup_pps(ctx, nal);
            if (err < 0)
                goto fail;
            if (!au_has_sps) {
                av_log(bsf, AV_LOG_VERBOSE, "Deleting redundant PPS "
                       "at %"PRId64".\n", pkt->pts);
                ff_cbs_delete_unit(au, i);
                i--;
                continue;
            }
        }
        if (nal->type == H264_NAL_SLICE ||
            nal->type == H264_NAL_IDR_SLICE) {
            H264RawSlice *slice = nal->content;
            h264_redundant_pps_fixup_slice(ctx, &slice->header);
        }
    }

    err = ff_cbs_write_packet(ctx->output, pkt, au);
    if (err < 0)
        goto fail;

    err = 0;
fail:
    ff_cbs_fragment_reset(au);
    if (err < 0)
        av_packet_unref(pkt);

    return err;
}

static int h264_redundant_pps_init(AVBSFContext *bsf)
{
    H264RedundantPPSContext *ctx = bsf->priv_data;
    CodedBitstreamFragment *au = &ctx->access_unit;
    int err, i;

    err = ff_cbs_init(&ctx->input, AV_CODEC_ID_H264, bsf);
    if (err < 0)
        return err;

    err = ff_cbs_init(&ctx->output, AV_CODEC_ID_H264, bsf);
    if (err < 0)
        return err;

    ctx->global_pic_init_qp = 26;

    if (bsf->par_in->extradata) {
        err = ff_cbs_read_extradata(ctx->input, au, bsf->par_in);
        if (err < 0) {
            av_log(bsf, AV_LOG_ERROR, "Failed to read extradata.\n");
            goto fail;
        }

        for (i = 0; i < au->nb_units; i++) {
            if (au->units[i].type == H264_NAL_PPS) {
                err = h264_redundant_pps_fixup_pps(ctx, &au->units[i]);
                if (err < 0)
                    goto fail;
            }
        }

        ctx->extradata_pic_init_qp = ctx->current_pic_init_qp;
        err = ff_cbs_write_extradata(ctx->output, bsf->par_out, au);
        if (err < 0) {
            av_log(bsf, AV_LOG_ERROR, "Failed to write extradata.\n");
            goto fail;
        }
    }

    err = 0;
fail:
    ff_cbs_fragment_reset(au);
    return err;
}

static void h264_redundant_pps_flush(AVBSFContext *bsf)
{
    H264RedundantPPSContext *ctx = bsf->priv_data;
    ctx->current_pic_init_qp = ctx->extradata_pic_init_qp;
}

static void h264_redundant_pps_close(AVBSFContext *bsf)
{
    H264RedundantPPSContext *ctx = bsf->priv_data;

    ff_cbs_fragment_free(&ctx->access_unit);
    ff_cbs_close(&ctx->input);
    ff_cbs_close(&ctx->output);
}

static const enum AVCodecID h264_redundant_pps_codec_ids[] = {
    AV_CODEC_ID_H264, AV_CODEC_ID_NONE,
};

const AVBitStreamFilter ff_h264_redundant_pps_bsf = {
    .name           = "h264_redundant_pps",
    .priv_data_size = sizeof(H264RedundantPPSContext),
    .init           = &h264_redundant_pps_init,
    .flush          = &h264_redundant_pps_flush,
    .close          = &h264_redundant_pps_close,
    .filter         = &h264_redundant_pps_filter,
    .codec_ids      = h264_redundant_pps_codec_ids,
};