| /* |
| * 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 "mpeg4video.h" |
| |
| typedef struct UnpackBFramesBSFContext { |
| uint8_t *b_frame_buf; |
| int b_frame_buf_size; |
| } UnpackBFramesBSFContext; |
| |
| /* search next start code */ |
| static unsigned int find_startcode(const uint8_t *buf, int buf_size, int *pos) |
| { |
| unsigned int startcode = 0xFF; |
| |
| for (; *pos < buf_size;) { |
| startcode = ((startcode << 8) | buf[*pos]) & 0xFFFFFFFF; |
| *pos +=1; |
| if ((startcode & 0xFFFFFF00) != 0x100) |
| continue; /* no startcode */ |
| return startcode; |
| } |
| |
| return 0; |
| } |
| |
| /* 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) { |
| unsigned int startcode; |
| int pos, i; |
| |
| for (pos = 0; pos < buf_size;) { |
| startcode = find_startcode(buf, buf_size, &pos); |
| |
| if (startcode == USER_DATA_STARTCODE && pos_p) { |
| /* check if the (DivX) userdata string ends with 'p' (packed) */ |
| for (i = 0; i < 255 && pos + i + 1 < buf_size; i++) { |
| if (buf[pos + i] == 'p' && buf[pos + i + 1] == '\0') { |
| *pos_p = pos + i; |
| break; |
| } |
| } |
| } else if (startcode == VOP_STARTCODE && nb_vop) { |
| *nb_vop += 1; |
| if (*nb_vop == 2 && pos_vop2) { |
| *pos_vop2 = pos - 4; /* subtract 4 bytes startcode */ |
| } |
| } |
| } |
| } |
| |
| /* allocate new buffer and copy size bytes from src */ |
| static uint8_t *create_new_buffer(const uint8_t *src, int size) { |
| uint8_t *dst = av_malloc(size + AV_INPUT_BUFFER_PADDING_SIZE); |
| |
| if (dst) { |
| memcpy(dst, src, size); |
| memset(dst + size, 0, AV_INPUT_BUFFER_PADDING_SIZE); |
| } |
| |
| return dst; |
| } |
| |
| static int mpeg4_unpack_bframes_filter(AVBSFContext *ctx, AVPacket *out) |
| { |
| UnpackBFramesBSFContext *s = ctx->priv_data; |
| int pos_p = -1, nb_vop = 0, pos_vop2 = -1, ret = 0; |
| AVPacket *in; |
| |
| ret = ff_bsf_get_packet(ctx, &in); |
| if (ret < 0) |
| return ret; |
| |
| scan_buffer(in->data, in->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_buf) { |
| av_log(ctx, AV_LOG_WARNING, |
| "Missing one N-VOP packet, discarding one B-frame.\n"); |
| av_freep(&s->b_frame_buf); |
| s->b_frame_buf_size = 0; |
| } |
| /* store the packed B-frame in the BSFContext */ |
| s->b_frame_buf_size = in->size - pos_vop2; |
| s->b_frame_buf = create_new_buffer(in->data + pos_vop2, s->b_frame_buf_size); |
| if (!s->b_frame_buf) { |
| s->b_frame_buf_size = 0; |
| av_packet_free(&in); |
| return AVERROR(ENOMEM); |
| } |
| } |
| |
| 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_buf) { |
| /* use frame from BSFContext */ |
| ret = av_packet_copy_props(out, in); |
| if (ret < 0) { |
| av_packet_free(&in); |
| return ret; |
| } |
| |
| ret = av_packet_from_data(out, s->b_frame_buf, s->b_frame_buf_size); |
| if (ret < 0) { |
| av_packet_free(&in); |
| return ret; |
| } |
| if (in->size <= MAX_NVOP_SIZE) { |
| /* N-VOP */ |
| av_log(ctx, AV_LOG_DEBUG, "Skipping N-VOP.\n"); |
| s->b_frame_buf = NULL; |
| s->b_frame_buf_size = 0; |
| } else { |
| /* copy packet into BSFContext */ |
| s->b_frame_buf_size = in->size; |
| s->b_frame_buf = create_new_buffer(in->data, in->size); |
| if (!s->b_frame_buf) { |
| s->b_frame_buf_size = 0; |
| av_packet_unref(out); |
| av_packet_free(&in); |
| return AVERROR(ENOMEM); |
| } |
| } |
| } else if (nb_vop >= 2) { |
| /* use first frame of the packet */ |
| av_packet_move_ref(out, in); |
| out->size = pos_vop2; |
| } else if (pos_p >= 0) { |
| av_log(ctx, AV_LOG_DEBUG, "Updating DivX userdata (remove trailing 'p').\n"); |
| av_packet_move_ref(out, in); |
| /* remove 'p' (packed) from the end of the (DivX) userdata string */ |
| out->data[pos_p] = '\0'; |
| } else { |
| /* copy packet */ |
| av_packet_move_ref(out, in); |
| } |
| |
| av_packet_free(&in); |
| |
| return 0; |
| } |
| |
| 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(AVBSFContext *bsfc) |
| { |
| UnpackBFramesBSFContext *ctx = bsfc->priv_data; |
| av_freep(&ctx->b_frame_buf); |
| } |
| |
| 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, |
| .close = mpeg4_unpack_bframes_close, |
| .codec_ids = codec_ids, |
| }; |