FFmpeg  4.3.9
mpeg4_unpack_bframes_bsf.c
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1 /*
2  * Bitstream filter for unpacking DivX-style packed B-frames in MPEG-4 (divx_packed)
3  * Copyright (c) 2015 Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "bsf.h"
23 #include "bsf_internal.h"
24 #include "internal.h"
25 #include "mpeg4video.h"
26 
27 typedef struct UnpackBFramesBSFContext {
30 
31 /* determine the position of the packed marker in the userdata,
32  * the number of VOPs and the position of the second VOP */
33 static void scan_buffer(const uint8_t *buf, int buf_size,
34  int *pos_p, int *nb_vop, int *pos_vop2) {
35  uint32_t startcode;
36  const uint8_t *end = buf + buf_size, *pos = buf;
37 
38  while (pos < end) {
39  startcode = -1;
40  pos = avpriv_find_start_code(pos, end, &startcode);
41 
42  if (startcode == USER_DATA_STARTCODE && pos_p) {
43  /* check if the (DivX) userdata string ends with 'p' (packed) */
44  for (int i = 0; i < 255 && pos + i + 1 < end; i++) {
45  if (pos[i] == 'p' && pos[i + 1] == '\0') {
46  *pos_p = pos + i - buf;
47  break;
48  }
49  }
50  } else if (startcode == VOP_STARTCODE && nb_vop) {
51  *nb_vop += 1;
52  if (*nb_vop == 2 && pos_vop2) {
53  *pos_vop2 = pos - buf - 4; /* subtract 4 bytes startcode */
54  }
55  }
56  }
57 }
58 
60 {
62  int pos_p = -1, nb_vop = 0, pos_vop2 = -1, ret = 0;
63 
64  ret = ff_bsf_get_packet_ref(ctx, pkt);
65  if (ret < 0)
66  return ret;
67 
68  scan_buffer(pkt->data, pkt->size, &pos_p, &nb_vop, &pos_vop2);
69  av_log(ctx, AV_LOG_DEBUG, "Found %d VOP startcode(s) in this packet.\n", nb_vop);
70 
71  if (pos_vop2 >= 0) {
72  if (s->b_frame_ref) {
74  "Missing one N-VOP packet, discarding one B-frame.\n");
76  }
77  /* store a reference to the packed B-frame's data in the BSFContext */
78  s->b_frame_ref = av_buffer_ref(pkt->buf);
79  if (!s->b_frame_ref) {
80  ret = AVERROR(ENOMEM);
81  goto fail;
82  }
83  s->b_frame_ref->data = pkt->data + pos_vop2;
84  s->b_frame_ref->size = pkt->size - pos_vop2;
85  }
86 
87  if (nb_vop > 2) {
89  "Found %d VOP headers in one packet, only unpacking one.\n", nb_vop);
90  }
91 
92  if (nb_vop == 1 && s->b_frame_ref) {
93  AVBufferRef *tmp = pkt->buf;
94 
95  /* make tmp accurately reflect the packet's data */
96  tmp->data = pkt->data;
97  tmp->size = pkt->size;
98 
99  /* replace data in packet with stored data */
100  pkt->buf = s->b_frame_ref;
101  pkt->data = s->b_frame_ref->data;
102  pkt->size = s->b_frame_ref->size;
103 
104  /* store reference to data into BSFContext */
105  s->b_frame_ref = tmp;
106 
107  if (s->b_frame_ref->size <= MAX_NVOP_SIZE) {
108  /* N-VOP - discard stored data */
109  av_log(ctx, AV_LOG_DEBUG, "Skipping N-VOP.\n");
111  }
112  } else if (nb_vop >= 2) {
113  /* use first frame of the packet */
114  pkt->size = pos_vop2;
115  } else if (pos_p >= 0) {
116  ret = av_packet_make_writable(pkt);
117  if (ret < 0)
118  goto fail;
119  av_log(ctx, AV_LOG_DEBUG, "Updating DivX userdata (remove trailing 'p').\n");
120  /* remove 'p' (packed) from the end of the (DivX) userdata string */
121  pkt->data[pos_p] = '\0';
122  } else {
123  /* use packet as is */
124  }
125 
126 fail:
127  if (ret < 0)
128  av_packet_unref(pkt);
129 
130  return ret;
131 }
132 
134 {
135  if (ctx->par_in->extradata) {
136  int pos_p_ext = -1;
137  scan_buffer(ctx->par_in->extradata, ctx->par_in->extradata_size, &pos_p_ext, NULL, NULL);
138  if (pos_p_ext >= 0) {
139  av_log(ctx, AV_LOG_DEBUG,
140  "Updating DivX userdata (remove trailing 'p') in extradata.\n");
141  ctx->par_out->extradata[pos_p_ext] = '\0';
142  }
143  }
144 
145  return 0;
146 }
147 
149 {
152 }
153 
154 static const enum AVCodecID codec_ids[] = {
156 };
157 
159  .name = "mpeg4_unpack_bframes",
160  .priv_data_size = sizeof(UnpackBFramesBSFContext),
165  .codec_ids = codec_ids,
166 };
#define NULL
Definition: coverity.c:32
AVCodecParameters * par_out
Parameters of the output stream.
Definition: bsf.h:83
void av_buffer_unref(AVBufferRef **buf)
Free a given reference and automatically free the buffer if there are no more references to it...
Definition: buffer.c:125
static void flush(AVCodecContext *avctx)
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:182
static av_cold int init(AVCodecContext *avctx)
Definition: avrndec.c:35
The bitstream filter state.
Definition: bsf.h:49
int size
Definition: packet.h:356
static AVPacket pkt
void * priv_data
Opaque filter-specific private data.
Definition: bsf.h:70
#define USER_DATA_STARTCODE
Definition: mpeg4video.h:62
static void filter(int16_t *output, ptrdiff_t out_stride, int16_t *low, ptrdiff_t low_stride, int16_t *high, ptrdiff_t high_stride, int len, int clip)
Definition: cfhd.c:196
uint8_t
const AVBitStreamFilter ff_mpeg4_unpack_bframes_bsf
#define VOP_STARTCODE
Definition: mpeg4video.h:65
static av_cold int end(AVCodecContext *avctx)
Definition: avrndec.c:92
static int mpeg4_unpack_bframes_filter(AVBSFContext *ctx, AVPacket *pkt)
const char * name
Definition: bsf.h:99
uint8_t * data
Definition: packet.h:355
#define av_log(a,...)
const uint8_t * avpriv_find_start_code(const uint8_t *p, const uint8_t *end, uint32_t *state)
int av_packet_make_writable(AVPacket *pkt)
Create a writable reference for the data described by a given packet, avoiding data copy if possible...
Definition: avpacket.c:690
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:269
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: codec_id.h:46
#define AVERROR(e)
Definition: error.h:43
unsigned int pos
Definition: spdifenc.c:412
#define AV_LOG_DEBUG
Stuff which is only useful for libav* developers.
Definition: log.h:197
AVBufferRef * buf
A reference to the reference-counted buffer where the packet data is stored.
Definition: packet.h:338
#define fail()
Definition: checkasm.h:123
int extradata_size
Size of the extradata content in bytes.
Definition: codec_par.h:78
static void mpeg4_unpack_bframes_close_flush(AVBSFContext *bsfc)
AVFormatContext * ctx
Definition: movenc.c:48
static int mpeg4_unpack_bframes_init(AVBSFContext *ctx)
#define s(width, name)
Definition: cbs_vp9.c:257
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:605
uint8_t * data
The data buffer.
Definition: buffer.h:89
static void scan_buffer(const uint8_t *buf, int buf_size, int *pos_p, int *nb_vop, int *pos_vop2)
int size
Size of data in bytes.
Definition: buffer.h:93
static enum AVCodecID codec_ids[]
A reference to a data buffer.
Definition: buffer.h:81
common internal api header.
AVBufferRef * av_buffer_ref(AVBufferRef *buf)
Create a new reference to an AVBuffer.
Definition: buffer.c:93
uint8_t * extradata
Extra binary data needed for initializing the decoder, codec-dependent.
Definition: codec_par.h:74
This structure stores compressed data.
Definition: packet.h:332
AVCodecParameters * par_in
Parameters of the input stream.
Definition: bsf.h:77
int ff_bsf_get_packet_ref(AVBSFContext *ctx, AVPacket *pkt)
Called by bitstream filters to get packet for filtering.
Definition: bsf.c:249
#define MAX_NVOP_SIZE
Definition: mpeg4video.h:72
static uint8_t tmp[11]
Definition: aes_ctr.c:26