/* * 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 "avcodec.h" #include "bsf.h" #include "internal.h" #include "mpeg4video.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 AVBitStreamFilter ff_mpeg4_unpack_bframes_bsf = { .name = "mpeg4_unpack_bframes", .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, .codec_ids = codec_ids, };