diff options
Diffstat (limited to 'libavcodec/mpeg4_unpack_bframes_bsf.c')
-rw-r--r-- | libavcodec/mpeg4_unpack_bframes_bsf.c | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/libavcodec/mpeg4_unpack_bframes_bsf.c b/libavcodec/mpeg4_unpack_bframes_bsf.c new file mode 100644 index 0000000..e227f58 --- /dev/null +++ b/libavcodec/mpeg4_unpack_bframes_bsf.c @@ -0,0 +1,201 @@ +/* + * 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, +}; |