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/*
* 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 "mpeg4videodefs.h"
#include "startcode.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 FFBitStreamFilter ff_mpeg4_unpack_bframes_bsf = {
.p.name = "mpeg4_unpack_bframes",
.p.codec_ids = codec_ids,
.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,
};
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