1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
|
/*
* 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 {
AVPacket *b_frame;
} 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 */
}
}
}
}
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->data) {
av_log(ctx, AV_LOG_WARNING,
"Missing one N-VOP packet, discarding one B-frame.\n");
av_packet_unref(s->b_frame);
}
/* store the packed B-frame in the BSFContext */
ret = av_packet_ref(s->b_frame, in);
if (ret < 0) {
goto fail;
}
s->b_frame->size -= pos_vop2;
s->b_frame->data += 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->data) {
/* use frame from BSFContext */
av_packet_move_ref(out, s->b_frame);
/* use properties from current input packet */
ret = av_packet_copy_props(out, in);
if (ret < 0) {
goto fail;
}
if (in->size <= MAX_NVOP_SIZE) {
/* N-VOP */
av_log(ctx, AV_LOG_DEBUG, "Skipping N-VOP.\n");
} else {
/* copy packet into BSFContext */
av_packet_move_ref(s->b_frame, in);
}
} 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) {
ret = av_packet_make_writable(in);
if (ret < 0)
goto fail;
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);
}
fail:
if (ret < 0)
av_packet_unref(out);
av_packet_free(&in);
return ret;
}
static int mpeg4_unpack_bframes_init(AVBSFContext *ctx)
{
UnpackBFramesBSFContext *s = ctx->priv_data;
s->b_frame = av_packet_alloc();
if (!s->b_frame)
return AVERROR(ENOMEM);
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_flush(AVBSFContext *bsfc)
{
UnpackBFramesBSFContext *ctx = bsfc->priv_data;
av_packet_unref(ctx->b_frame);
}
static void mpeg4_unpack_bframes_close(AVBSFContext *bsfc)
{
UnpackBFramesBSFContext *ctx = bsfc->priv_data;
av_packet_free(&ctx->b_frame);
}
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_flush,
.close = mpeg4_unpack_bframes_close,
.codec_ids = codec_ids,
};
|
