| /* |
| * 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 "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, |
| }; |