FFmpeg
data_uri.c
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1 /*
2  * Copyright (c) 2012 Nicolas George
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public License
8  * as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  * GNU Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public License
17  * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #include <string.h>
22 #include "libavutil/avstring.h"
23 #include "libavutil/base64.h"
24 #include "url.h"
25 
26 typedef struct {
27  const uint8_t *data;
28  void *tofree;
29  size_t size;
30  size_t pos;
31 } DataContext;
32 
33 static av_cold int data_open(URLContext *h, const char *uri, int flags)
34 {
35  DataContext *dc = h->priv_data;
36  const char *data, *opt, *next;
37  char *ddata;
38  int ret, base64 = 0;
39  size_t in_size;
40 
41  /* data:content/type[;base64],payload */
42 
43  av_strstart(uri, "data:", &uri);
44  data = strchr(uri, ',');
45  if (!data) {
46  av_log(h, AV_LOG_ERROR, "No ',' delimiter in URI\n");
47  return AVERROR(EINVAL);
48  }
49  opt = uri;
50  while (opt < data) {
51  next = av_x_if_null(memchr(opt, ';', data - opt), data);
52  if (opt == uri) {
53  if (!memchr(opt, '/', next - opt)) { /* basic validity check */
54  av_log(h, AV_LOG_ERROR, "Invalid content-type '%.*s'\n",
55  (int)(next - opt), opt);
56  return AVERROR(EINVAL);
57  }
58  av_log(h, AV_LOG_VERBOSE, "Content-type: %.*s\n",
59  (int)(next - opt), opt);
60  } else {
61  if (!av_strncasecmp(opt, "base64", next - opt)) {
62  base64 = 1;
63  } else {
64  av_log(h, AV_LOG_VERBOSE, "Ignoring option '%.*s'\n",
65  (int)(next - opt), opt);
66  }
67  }
68  opt = next + 1;
69  }
70 
71  data++;
72  in_size = strlen(data);
73  if (base64) {
74  size_t out_size = 3 * (in_size / 4) + 1;
75 
76  if (out_size > INT_MAX || !(ddata = av_malloc(out_size)))
77  return AVERROR(ENOMEM);
78  if ((ret = av_base64_decode(ddata, data, out_size)) < 0) {
79  av_free(ddata);
80  av_log(h, AV_LOG_ERROR, "Invalid base64 in URI\n");
81  return ret;
82  }
83  dc->data = dc->tofree = ddata;
84  dc->size = ret;
85  } else {
86  dc->data = data;
87  dc->size = in_size;
88  }
89  return 0;
90 }
91 
93 {
94  DataContext *dc = h->priv_data;
95 
96  av_freep(&dc->tofree);
97  return 0;
98 }
99 
100 static int data_read(URLContext *h, unsigned char *buf, int size)
101 {
102  DataContext *dc = h->priv_data;
103 
104  if (dc->pos >= dc->size)
105  return AVERROR_EOF;
106  size = FFMIN(size, dc->size - dc->pos);
107  memcpy(buf, dc->data + dc->pos, size);
108  dc->pos += size;
109  return size;
110 }
111 
113  .name = "data",
114  .url_open = data_open,
115  .url_close = data_close,
116  .url_read = data_read,
117  .priv_data_size = sizeof(DataContext),
118 };
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
AVERROR_EOF
#define AVERROR_EOF
End of file.
Definition: error.h:55
data_open
static av_cold int data_open(URLContext *h, const char *uri, int flags)
Definition: data_uri.c:33
data_close
static av_cold int data_close(URLContext *h)
Definition: data_uri.c:92
out_size
int out_size
Definition: movenc.c:55
data
const char data[16]
Definition: mxf.c:142
AV_LOG_VERBOSE
#define AV_LOG_VERBOSE
Detailed information.
Definition: log.h:197
DataContext::tofree
void * tofree
Definition: data_uri.c:28
URLProtocol
Definition: url.h:54
av_malloc
#define av_malloc(s)
Definition: tableprint_vlc.h:31
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:181
av_cold
#define av_cold
Definition: attributes.h:90
Frame::pos
int64_t pos
Definition: ffplay.c:161
av_base64_decode
int av_base64_decode(uint8_t *out, const char *in_str, int out_size)
Decode a base64-encoded string.
Definition: base64.c:79
base64.h
av_strncasecmp
int av_strncasecmp(const char *a, const char *b, size_t n)
Locale-independent case-insensitive compare.
Definition: avstring.c:225
dc
Tag MUST be and< 10hcoeff half pel interpolation filter coefficients, hcoeff[0] are the 2 middle coefficients[1] are the next outer ones and so on, resulting in a filter like:...eff[2], hcoeff[1], hcoeff[0], hcoeff[0], hcoeff[1], hcoeff[2] ... the sign of the coefficients is not explicitly stored but alternates after each coeff and coeff[0] is positive, so ...,+,-,+,-,+,+,-,+,-,+,... hcoeff[0] is not explicitly stored but found by subtracting the sum of all stored coefficients with signs from 32 hcoeff[0]=32 - hcoeff[1] - hcoeff[2] - ... a good choice for hcoeff and htaps is htaps=6 hcoeff={40,-10, 2} an alternative which requires more computations at both encoder and decoder side and may or may not be better is htaps=8 hcoeff={42,-14, 6,-2}ref_frames minimum of the number of available reference frames and max_ref_frames for example the first frame after a key frame always has ref_frames=1spatial_decomposition_type wavelet type 0 is a 9/7 symmetric compact integer wavelet 1 is a 5/3 symmetric compact integer wavelet others are reserved stored as delta from last, last is reset to 0 if always_reset||keyframeqlog quality(logarithmic quantizer scale) stored as delta from last, last is reset to 0 if always_reset||keyframemv_scale stored as delta from last, last is reset to 0 if always_reset||keyframe FIXME check that everything works fine if this changes between framesqbias dequantization bias stored as delta from last, last is reset to 0 if always_reset||keyframeblock_max_depth maximum depth of the block tree stored as delta from last, last is reset to 0 if always_reset||keyframequant_table quantization tableHighlevel bitstream structure:==============================--------------------------------------------|Header|--------------------------------------------|------------------------------------|||Block0||||split?||||yes no||||......... intra?||||:Block01 :yes no||||:Block02 :....... ..........||||:Block03 ::y DC ::ref index:||||:Block04 ::cb DC ::motion x :||||......... :cr DC ::motion y :||||....... ..........|||------------------------------------||------------------------------------|||Block1|||...|--------------------------------------------|------------ ------------ ------------|||Y subbands||Cb subbands||Cr subbands||||--- ---||--- ---||--- ---|||||LL0||HL0||||LL0||HL0||||LL0||HL0|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||LH0||HH0||||LH0||HH0||||LH0||HH0|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||HL1||LH1||||HL1||LH1||||HL1||LH1|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||HH1||HL2||||HH1||HL2||||HH1||HL2|||||...||...||...|||------------ ------------ ------------|--------------------------------------------Decoding process:=================------------|||Subbands|------------||||------------|Intra DC||||LL0 subband prediction ------------|\ Dequantization ------------------- \||Reference frames|\ IDWT|------- -------|Motion \|||Frame 0||Frame 1||Compensation . OBMC v -------|------- -------|--------------. \------> Frame n output Frame Frame<----------------------------------/|...|------------------- Range Coder:============Binary Range Coder:------------------- The implemented range coder is an adapted version based upon "Range encoding: an algorithm for removing redundancy from a digitised message." by G. N. N. Martin. The symbols encoded by the Snow range coder are bits(0|1). The associated probabilities are not fix but change depending on the symbol mix seen so far. bit seen|new state ---------+----------------------------------------------- 0|256 - state_transition_table[256 - old_state];1|state_transition_table[old_state];state_transition_table={ 0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 190, 191, 192, 194, 194, 195, 196, 197, 198, 199, 200, 201, 202, 202, 204, 205, 206, 207, 208, 209, 209, 210, 211, 212, 213, 215, 215, 216, 217, 218, 219, 220, 220, 222, 223, 224, 225, 226, 227, 227, 229, 229, 230, 231, 232, 234, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 248, 0, 0, 0, 0, 0, 0, 0};FIXME Range Coding of integers:------------------------- FIXME Neighboring Blocks:===================left and top are set to the respective blocks unless they are outside of the image in which case they are set to the Null block top-left is set to the top left block unless it is outside of the image in which case it is set to the left block if this block has no larger parent block or it is at the left side of its parent block and the top right block is not outside of the image then the top right block is used for top-right else the top-left block is used Null block y, cb, cr are 128 level, ref, mx and my are 0 Motion Vector Prediction:=========================1. the motion vectors of all the neighboring blocks are scaled to compensate for the difference of reference frames scaled_mv=(mv *(256 *(current_reference+1)/(mv.reference+1))+128)> the median of the scaled top and top right vectors is used as motion vector prediction the used motion vector is the sum of the predictor and(mvx_diff, mvy_diff) *mv_scale Intra DC Prediction block[y][x] dc[1]
Definition: snow.txt:400
size
int size
Definition: twinvq_data.h:10344
ff_data_protocol
const URLProtocol ff_data_protocol
Definition: data_uri.c:112
URLProtocol::name
const char * name
Definition: url.h:55
FFMIN
#define FFMIN(a, b)
Definition: common.h:105
av_strstart
int av_strstart(const char *str, const char *pfx, const char **ptr)
Return non-zero if pfx is a prefix of str.
Definition: avstring.c:34
DataContext::pos
size_t pos
Definition: data_uri.c:30
URLContext
Definition: url.h:38
url.h
data_read
static int data_read(URLContext *h, unsigned char *buf, int size)
Definition: data_uri.c:100
DataContext::data
const uint8_t * data
Definition: data_uri.c:27
ret
ret
Definition: filter_design.txt:187
DataContext::size
size_t size
Definition: data_uri.c:29
av_free
#define av_free(p)
Definition: tableprint_vlc.h:34
av_freep
#define av_freep(p)
Definition: tableprint_vlc.h:35
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
h
h
Definition: vp9dsp_template.c:2038
avstring.h
DataContext
Definition: data_uri.c:26
av_x_if_null
static void * av_x_if_null(const void *p, const void *x)
Return x default pointer in case p is NULL.
Definition: avutil.h:308