Go to the documentation of this file. 1 /*
2 * xWMA demuxer
3 * Copyright (c) 2011 Max Horn
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 <inttypes.h>
23 #include <stdint.h>
24
28
29 /*
30 * Demuxer for xWMA, a Microsoft audio container used by XAudio 2.
31 */
32
36
38 {
39 if (!memcmp(p->
buf,
"RIFF", 4) && !memcmp(p->
buf + 8,
"XWMA", 4))
41 return 0;
42 }
43
45 {
48 uint32_t dpds_table_size = 0;
49 uint32_t *dpds_table =
NULL;
55
56 /* The following code is mostly copied from wav.c, with some
57 * minor alterations.
58 */
59
60 /* check RIFF header */
62 if (
tag !=
MKTAG(
'R',
'I',
'F',
'F'))
66 if (
tag !=
MKTAG(
'X',
'W',
'M',
'A'))
68
69 /* parse fmt header */
71 if (
tag !=
MKTAG(
'f',
'm',
't',
' '))
75 if (!st)
77
82
83 /* XWMA encoder only allows a few channel/sample rate/bitrate combinations,
84 * but some create identical files with fake bitrate (1ch 22050hz at
85 * 20/48/192kbps are all 20kbps, with the exact same codec data).
86 * Decoder needs correct bitrate to work, so it's normalized here. */
91
92 if (ch == 1) {
93 if (sr == 22050 && (br==48000 || br==192000))
94 br = 20000;
95 else if (sr == 32000 && (br==48000 || br==192000))
96 br = 20000;
97 else if (sr == 44100 && (br==96000 || br==192000))
98 br = 48000;
99 }
100 else if (ch == 2) {
101 if (sr == 22050 && (br==48000 || br==192000))
102 br = 32000;
103 else if (sr == 32000 && (br==192000))
104 br = 48000;
105 }
106
108 }
109
110 /* Normally xWMA can only contain WMAv2 with 1/2 channels,
111 * and WMAPRO with 6 channels. */
117 } else {
118 /* xWMA shouldn't have extradata. But the WMA codecs require it,
119 * so we provide our own fake extradata.
120 *
121 * First, check that there really was no extradata in the header. If
122 * there was, then try to use it, after asking the user to provide a
123 * sample of this unusual file.
124 */
126 /* Surprise, surprise: We *did* get some extradata. No idea
127 * if it will work, but just go on and try it, after asking
128 * the user for a sample.
129 */
135
139 } else {
142
144 /* setup extradata with our experimentally obtained value */
146 }
147 }
148
153 }
158 }
159
160 /* set the sample rate */
162
163 /* parse the remaining RIFF chunks */
164 for (;;) {
168 }
169 /* read next chunk tag */
172 if (
tag ==
MKTAG(
'd',
'a',
't',
'a')) {
173 /* We assume that the data chunk comes last. */
174 break;
175 }
else if (
tag ==
MKTAG(
'd',
'p',
'd',
's')) {
176 /* Quoting the MSDN xWMA docs on the dpds chunk: "Contains the
177 * decoded packet cumulative data size array, each element is the
178 * number of bytes accumulated after the corresponding xWMA packet
179 * is decoded in order."
180 *
181 * Each packet has size equal to st->codecpar->block_align, which in
182 * all cases I saw so far was always 2230. Thus, we can use the
183 * dpds data to compute a seeking index.
184 */
185
186 /* Error out if there is more than one dpds chunk. */
187 if (dpds_table) {
191 }
192
193 /* Compute the number of entries in the dpds chunk. */
194 if (
size & 3) {
/* Size should be divisible by four */
196 "dpds chunk size %"PRId64
" not divisible by 4\n",
size);
197 }
198 dpds_table_size =
size / 4;
199 if (dpds_table_size == 0 || dpds_table_size >= INT_MAX / 4) {
201 "dpds chunk size %"PRId64
" invalid\n",
size);
203 }
204
205 /* Allocate some temporary storage to keep the dpds data around.
206 * for processing later on.
207 */
209 if (!dpds_table) {
211 }
212
213 for (
i = 0;
i < dpds_table_size; ++
i) {
217 }
220 }
221 }
223 }
224
225 /* Determine overall data length */
229 }
232 } else
234
235
236 if (dpds_table && dpds_table_size) {
237 int64_t cur_pos;
238 const uint32_t bytes_per_sample
240
241 /* Estimate the duration from the total number of output bytes. */
242 const uint64_t total_decoded_bytes = dpds_table[dpds_table_size - 1];
243
244 if (!bytes_per_sample) {
246 "Invalid bits_per_coded_sample %d for %d channels\n",
250 }
251
252 st->
duration = total_decoded_bytes / bytes_per_sample;
253
254 /* Use the dpds data to build a seek table. We can only do this after
255 * we know the offset to the data chunk, as we need that to determine
256 * the actual offset to each input block.
257 * Note: If we allowed ourselves to assume that the data chunk always
258 * follows immediately after the dpds block, we could of course guess
259 * the data block's start offset already while reading the dpds chunk.
260 * I decided against that, just in case other chunks ever are
261 * discovered.
262 */
264 for (
i = 0;
i < dpds_table_size; ++
i) {
265 /* From the number of output bytes that would accumulate in the
266 * output buffer after decoding the first (i+1) packets, we compute
267 * an offset / timestamp pair.
268 */
271 dpds_table[
i] / bytes_per_sample,
/* timestamp */
273 0, /* duration */
275 }
277 /* No dpds chunk was present (or only an empty one), so estimate
278 * the total duration using the average bits per sample and the
279 * total data length.
280 */
282 }
283
286
288 }
289
291 {
296
298
302 }
303
304 /* read a single block; the default block size is 2230. */
307
311
314 }
315
323 };
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 left