/* * Bitstream filter for unpacking DivX-style packed B-frames in MPEG-4 (divx_packed) * Copyright (c) 2015 Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.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 */ #include "bsf.h"#include "bsf_internal.h"#include "mpeg4videodefs.h"#include "startcode.h" typedef struct UnpackBFramesBSFContext {    AVBufferRef *b_frame_ref;} UnpackBFramesBSFContext; /* determine the position of the packed marker in the userdata, * the number of VOPs and the position of the second VOP */static void scan_buffer(const uint8_t *buf, int buf_size,                        int *pos_p, int *nb_vop, int *pos_vop2) {    uint32_t startcode;    const uint8_t *end = buf + buf_size, *pos = buf;     while (pos < end) {        startcode = -1;        pos = avpriv_find_start_code(pos, end, &startcode);         if (startcode == USER_DATA_STARTCODE && pos_p) {            /* check if the (DivX) userdata string ends with 'p' (packed) */            for (int i = 0; i < 255 && pos + i + 1 < end; i++) {                if (pos[i] == 'p' && pos[i + 1] == '\0') {                    *pos_p = pos + i - buf;                    break;                }            }        } else if (startcode == VOP_STARTCODE && nb_vop) {            *nb_vop += 1;            if (*nb_vop == 2 && pos_vop2) {                *pos_vop2 = pos - buf - 4; /* subtract 4 bytes startcode */            }        }    }} static int mpeg4_unpack_bframes_filter(AVBSFContext *ctx, AVPacket *pkt){    UnpackBFramesBSFContext *s = ctx->priv_data;    int pos_p = -1, nb_vop = 0, pos_vop2 = -1, ret = 0;     ret = ff_bsf_get_packet_ref(ctx, pkt);    if (ret < 0)        return ret;     scan_buffer(pkt->data, pkt->size, &pos_p, &nb_vop, &pos_vop2);    av_log(ctx, AV_LOG_DEBUG, "Found %d VOP startcode(s) in this packet.\n", nb_vop);     if (pos_vop2 >= 0) {        if (s->b_frame_ref) {            av_log(ctx, AV_LOG_WARNING,                   "Missing one N-VOP packet, discarding one B-frame.\n");            av_buffer_unref(&s->b_frame_ref);        }        /* store a reference to the packed B-frame's data in the BSFContext */        s->b_frame_ref = av_buffer_ref(pkt->buf);        if (!s->b_frame_ref) {            ret = AVERROR(ENOMEM);            goto fail;        }        s->b_frame_ref->data = pkt->data + pos_vop2;        s->b_frame_ref->size = pkt->size - pos_vop2;    }     if (nb_vop > 2) {        av_log(ctx, AV_LOG_WARNING,       "Found %d VOP headers in one packet, only unpacking one.\n", nb_vop);    }     if (nb_vop == 1 && s->b_frame_ref) {        AVBufferRef *tmp = pkt->buf;         /* make tmp accurately reflect the packet's data */        tmp->data = pkt->data;        tmp->size = pkt->size;         /* replace data in packet with stored data */        pkt->buf  = s->b_frame_ref;        pkt->data = s->b_frame_ref->data;        pkt->size = s->b_frame_ref->size;         /* store reference to data into BSFContext */        s->b_frame_ref = tmp;         if (s->b_frame_ref->size <= MAX_NVOP_SIZE) {            /* N-VOP - discard stored data */            av_log(ctx, AV_LOG_DEBUG, "Skipping N-VOP.\n");            av_buffer_unref(&s->b_frame_ref);        }    } else if (nb_vop >= 2) {        /* use first frame of the packet */        pkt->size = pos_vop2;    } else if (pos_p >= 0) {        ret = av_packet_make_writable(pkt);        if (ret < 0)            goto fail;        av_log(ctx, AV_LOG_DEBUG, "Updating DivX userdata (remove trailing 'p').\n");        /* remove 'p' (packed) from the end of the (DivX) userdata string */        pkt->data[pos_p] = '\0';    } else {        /* use packet as is */    } fail:    if (ret < 0)        av_packet_unref(pkt);     return ret;} static int mpeg4_unpack_bframes_init(AVBSFContext *ctx){    if (ctx->par_in->extradata) {        int pos_p_ext = -1;        scan_buffer(ctx->par_in->extradata, ctx->par_in->extradata_size, &pos_p_ext, NULL, NULL);        if (pos_p_ext >= 0) {            av_log(ctx, AV_LOG_DEBUG,                   "Updating DivX userdata (remove trailing 'p') in extradata.\n");            ctx->par_out->extradata[pos_p_ext] = '\0';        }    }     return 0;} static void mpeg4_unpack_bframes_close_flush(AVBSFContext *bsfc){    UnpackBFramesBSFContext *ctx = bsfc->priv_data;    av_buffer_unref(&ctx->b_frame_ref);} static const enum AVCodecID codec_ids[] = {    AV_CODEC_ID_MPEG4, AV_CODEC_ID_NONE,}; const FFBitStreamFilter ff_mpeg4_unpack_bframes_bsf = {    .p.name         = "mpeg4_unpack_bframes",    .p.codec_ids    = codec_ids,    .priv_data_size = sizeof(UnpackBFramesBSFContext),    .init           = mpeg4_unpack_bframes_init,    .filter         = mpeg4_unpack_bframes_filter,    .flush          = mpeg4_unpack_bframes_close_flush,    .close          = mpeg4_unpack_bframes_close_flush,};