mirror of
https://github.com/FFmpeg/FFmpeg.git
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e5b1f2b027
Signed-off-by: James Almer <jamrial@gmail.com>
194 lines
5.9 KiB
C
194 lines
5.9 KiB
C
/*
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* Bitstream filter for unpacking DivX-style packed B-frames in MPEG-4 (divx_packed)
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* Copyright (c) 2015 Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "avcodec.h"
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#include "bsf.h"
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#include "mpeg4video.h"
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typedef struct UnpackBFramesBSFContext {
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AVPacket *b_frame;
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} UnpackBFramesBSFContext;
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/* search next start code */
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static unsigned int find_startcode(const uint8_t *buf, int buf_size, int *pos)
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{
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unsigned int startcode = 0xFF;
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for (; *pos < buf_size;) {
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startcode = ((startcode << 8) | buf[*pos]) & 0xFFFFFFFF;
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*pos +=1;
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if ((startcode & 0xFFFFFF00) != 0x100)
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continue; /* no startcode */
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return startcode;
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}
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return 0;
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}
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/* determine the position of the packed marker in the userdata,
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* the number of VOPs and the position of the second VOP */
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static void scan_buffer(const uint8_t *buf, int buf_size,
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int *pos_p, int *nb_vop, int *pos_vop2) {
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unsigned int startcode;
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int pos, i;
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for (pos = 0; pos < buf_size;) {
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startcode = find_startcode(buf, buf_size, &pos);
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if (startcode == USER_DATA_STARTCODE && pos_p) {
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/* check if the (DivX) userdata string ends with 'p' (packed) */
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for (i = 0; i < 255 && pos + i + 1 < buf_size; i++) {
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if (buf[pos + i] == 'p' && buf[pos + i + 1] == '\0') {
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*pos_p = pos + i;
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break;
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}
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}
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} else if (startcode == VOP_STARTCODE && nb_vop) {
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*nb_vop += 1;
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if (*nb_vop == 2 && pos_vop2) {
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*pos_vop2 = pos - 4; /* subtract 4 bytes startcode */
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}
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}
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}
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}
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static int mpeg4_unpack_bframes_filter(AVBSFContext *ctx, AVPacket *out)
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{
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UnpackBFramesBSFContext *s = ctx->priv_data;
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int pos_p = -1, nb_vop = 0, pos_vop2 = -1, ret = 0;
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AVPacket *in;
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ret = ff_bsf_get_packet(ctx, &in);
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if (ret < 0)
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return ret;
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scan_buffer(in->data, in->size, &pos_p, &nb_vop, &pos_vop2);
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av_log(ctx, AV_LOG_DEBUG, "Found %d VOP startcode(s) in this packet.\n", nb_vop);
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if (pos_vop2 >= 0) {
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if (s->b_frame->data) {
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av_log(ctx, AV_LOG_WARNING,
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"Missing one N-VOP packet, discarding one B-frame.\n");
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av_packet_unref(s->b_frame);
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}
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/* store the packed B-frame in the BSFContext */
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ret = av_packet_ref(s->b_frame, in);
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if (ret < 0) {
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goto fail;
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}
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s->b_frame->size -= pos_vop2;
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s->b_frame->data += pos_vop2;
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}
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if (nb_vop > 2) {
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av_log(ctx, AV_LOG_WARNING,
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"Found %d VOP headers in one packet, only unpacking one.\n", nb_vop);
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}
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if (nb_vop == 1 && s->b_frame->data) {
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/* use frame from BSFContext */
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av_packet_move_ref(out, s->b_frame);
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/* use properties from current input packet */
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ret = av_packet_copy_props(out, in);
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if (ret < 0) {
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goto fail;
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}
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if (in->size <= MAX_NVOP_SIZE) {
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/* N-VOP */
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av_log(ctx, AV_LOG_DEBUG, "Skipping N-VOP.\n");
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} else {
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/* copy packet into BSFContext */
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av_packet_move_ref(s->b_frame, in);
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}
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} else if (nb_vop >= 2) {
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/* use first frame of the packet */
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av_packet_move_ref(out, in);
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out->size = pos_vop2;
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} else if (pos_p >= 0) {
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ret = av_packet_make_writable(in);
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if (ret < 0)
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goto fail;
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av_log(ctx, AV_LOG_DEBUG, "Updating DivX userdata (remove trailing 'p').\n");
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av_packet_move_ref(out, in);
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/* remove 'p' (packed) from the end of the (DivX) userdata string */
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out->data[pos_p] = '\0';
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} else {
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/* copy packet */
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av_packet_move_ref(out, in);
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}
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fail:
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if (ret < 0)
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av_packet_unref(out);
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av_packet_free(&in);
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return ret;
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}
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static int mpeg4_unpack_bframes_init(AVBSFContext *ctx)
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{
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UnpackBFramesBSFContext *s = ctx->priv_data;
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s->b_frame = av_packet_alloc();
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if (!s->b_frame)
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return AVERROR(ENOMEM);
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if (ctx->par_in->extradata) {
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int pos_p_ext = -1;
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scan_buffer(ctx->par_in->extradata, ctx->par_in->extradata_size, &pos_p_ext, NULL, NULL);
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if (pos_p_ext >= 0) {
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av_log(ctx, AV_LOG_DEBUG,
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"Updating DivX userdata (remove trailing 'p') in extradata.\n");
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ctx->par_out->extradata[pos_p_ext] = '\0';
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}
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}
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return 0;
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}
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static void mpeg4_unpack_bframes_flush(AVBSFContext *bsfc)
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{
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UnpackBFramesBSFContext *ctx = bsfc->priv_data;
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av_packet_unref(ctx->b_frame);
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}
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static void mpeg4_unpack_bframes_close(AVBSFContext *bsfc)
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{
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UnpackBFramesBSFContext *ctx = bsfc->priv_data;
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av_packet_free(&ctx->b_frame);
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}
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static const enum AVCodecID codec_ids[] = {
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AV_CODEC_ID_MPEG4, AV_CODEC_ID_NONE,
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};
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const AVBitStreamFilter ff_mpeg4_unpack_bframes_bsf = {
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.name = "mpeg4_unpack_bframes",
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.priv_data_size = sizeof(UnpackBFramesBSFContext),
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.init = mpeg4_unpack_bframes_init,
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.filter = mpeg4_unpack_bframes_filter,
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.flush = mpeg4_unpack_bframes_flush,
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.close = mpeg4_unpack_bframes_close,
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.codec_ids = codec_ids,
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};
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