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xwma.c
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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 
24 #include "avformat.h"
25 #include "internal.h"
26 #include "riff.h"
27 
28 /*
29  * Demuxer for xWMA, a Microsoft audio container used by XAudio 2.
30  */
31 
32 typedef struct {
33  int64_t data_end;
34 } XWMAContext;
35 
36 static int xwma_probe(AVProbeData *p)
37 {
38  if (!memcmp(p->buf, "RIFF", 4) && !memcmp(p->buf + 8, "XWMA", 4))
39  return AVPROBE_SCORE_MAX;
40  return 0;
41 }
42 
44 {
45  int64_t size;
46  int ret;
47  uint32_t dpds_table_size = 0;
48  uint32_t *dpds_table = 0;
49  unsigned int tag;
50  AVIOContext *pb = s->pb;
51  AVStream *st;
52  XWMAContext *xwma = s->priv_data;
53  int i;
54 
55  /* The following code is mostly copied from wav.c, with some
56  * minor alterations.
57  */
58 
59  /* check RIFF header */
60  tag = avio_rl32(pb);
61  if (tag != MKTAG('R', 'I', 'F', 'F'))
62  return -1;
63  avio_rl32(pb); /* file size */
64  tag = avio_rl32(pb);
65  if (tag != MKTAG('X', 'W', 'M', 'A'))
66  return -1;
67 
68  /* parse fmt header */
69  tag = avio_rl32(pb);
70  if (tag != MKTAG('f', 'm', 't', ' '))
71  return -1;
72  size = avio_rl32(pb);
73  st = avformat_new_stream(s, NULL);
74  if (!st)
75  return AVERROR(ENOMEM);
76 
77  ret = ff_get_wav_header(pb, st->codec, size);
78  if (ret < 0)
79  return ret;
81 
82  /* All xWMA files I have seen contained WMAv2 data. If there are files
83  * using WMA Pro or some other codec, then we need to figure out the right
84  * extradata for that. Thus, ask the user for feedback, but try to go on
85  * anyway.
86  */
87  if (st->codec->codec_id != AV_CODEC_ID_WMAV2) {
88  av_log(s, AV_LOG_WARNING, "unexpected codec (tag 0x04%x; id %d)\n",
89  st->codec->codec_tag, st->codec->codec_id);
91  } else {
92  /* In all xWMA files I have seen, there is no extradata. But the WMA
93  * codecs require extradata, so we provide our own fake extradata.
94  *
95  * First, check that there really was no extradata in the header. If
96  * there was, then try to use it, after asking the user to provide a
97  * sample of this unusual file.
98  */
99  if (st->codec->extradata_size != 0) {
100  /* Surprise, surprise: We *did* get some extradata. No idea
101  * if it will work, but just go on and try it, after asking
102  * the user for a sample.
103  */
104  av_log(s, AV_LOG_WARNING, "unexpected extradata (%d bytes)\n",
105  st->codec->extradata_size);
107  } else {
108  st->codec->extradata_size = 6;
110  if (!st->codec->extradata)
111  return AVERROR(ENOMEM);
112 
113  /* setup extradata with our experimentally obtained value */
114  st->codec->extradata[4] = 31;
115  }
116  }
117 
118  if (!st->codec->channels) {
119  av_log(s, AV_LOG_WARNING, "Invalid channel count: %d\n",
120  st->codec->channels);
121  return AVERROR_INVALIDDATA;
122  }
123  if (!st->codec->bits_per_coded_sample) {
124  av_log(s, AV_LOG_WARNING, "Invalid bits_per_coded_sample: %d\n",
126  return AVERROR_INVALIDDATA;
127  }
128 
129  /* set the sample rate */
130  avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);
131 
132  /* parse the remaining RIFF chunks */
133  for (;;) {
134  if (pb->eof_reached)
135  return -1;
136  /* read next chunk tag */
137  tag = avio_rl32(pb);
138  size = avio_rl32(pb);
139  if (tag == MKTAG('d', 'a', 't', 'a')) {
140  /* We assume that the data chunk comes last. */
141  break;
142  } else if (tag == MKTAG('d','p','d','s')) {
143  /* Quoting the MSDN xWMA docs on the dpds chunk: "Contains the
144  * decoded packet cumulative data size array, each element is the
145  * number of bytes accumulated after the corresponding xWMA packet
146  * is decoded in order."
147  *
148  * Each packet has size equal to st->codec->block_align, which in
149  * all cases I saw so far was always 2230. Thus, we can use the
150  * dpds data to compute a seeking index.
151  */
152 
153  /* Error out if there is more than one dpds chunk. */
154  if (dpds_table) {
155  av_log(s, AV_LOG_ERROR, "two dpds chunks present\n");
156  return -1;
157  }
158 
159  /* Compute the number of entries in the dpds chunk. */
160  if (size & 3) { /* Size should be divisible by four */
162  "dpds chunk size %"PRId64" not divisible by 4\n", size);
163  }
164  dpds_table_size = size / 4;
165  if (dpds_table_size == 0 || dpds_table_size >= INT_MAX / 4) {
166  av_log(s, AV_LOG_ERROR,
167  "dpds chunk size %"PRId64" invalid\n", size);
168  return -1;
169  }
170 
171  /* Allocate some temporary storage to keep the dpds data around.
172  * for processing later on.
173  */
174  dpds_table = av_malloc(dpds_table_size * sizeof(uint32_t));
175  if (!dpds_table) {
176  return AVERROR(ENOMEM);
177  }
178 
179  for (i = 0; i < dpds_table_size; ++i) {
180  dpds_table[i] = avio_rl32(pb);
181  size -= 4;
182  }
183  }
184  avio_skip(pb, size);
185  }
186 
187  /* Determine overall data length */
188  if (size < 0)
189  return -1;
190  if (!size) {
191  xwma->data_end = INT64_MAX;
192  } else
193  xwma->data_end = avio_tell(pb) + size;
194 
195 
196  if (dpds_table && dpds_table_size) {
197  int64_t cur_pos;
198  const uint32_t bytes_per_sample
199  = (st->codec->channels * st->codec->bits_per_coded_sample) >> 3;
200 
201  /* Estimate the duration from the total number of output bytes. */
202  const uint64_t total_decoded_bytes = dpds_table[dpds_table_size - 1];
203 
204  if(!bytes_per_sample) {
205  av_log(s, AV_LOG_ERROR, "bytes_per_sample is 0\n");
206  return AVERROR_INVALIDDATA;
207  }
208 
209  st->duration = total_decoded_bytes / bytes_per_sample;
210 
211  /* Use the dpds data to build a seek table. We can only do this after
212  * we know the offset to the data chunk, as we need that to determine
213  * the actual offset to each input block.
214  * Note: If we allowed ourselves to assume that the data chunk always
215  * follows immediately after the dpds block, we could of course guess
216  * the data block's start offset already while reading the dpds chunk.
217  * I decided against that, just in case other chunks ever are
218  * discovered.
219  */
220  cur_pos = avio_tell(pb);
221  for (i = 0; i < dpds_table_size; ++i) {
222  /* From the number of output bytes that would accumulate in the
223  * output buffer after decoding the first (i+1) packets, we compute
224  * an offset / timestamp pair.
225  */
227  cur_pos + (i+1) * st->codec->block_align, /* pos */
228  dpds_table[i] / bytes_per_sample, /* timestamp */
229  st->codec->block_align, /* size */
230  0, /* duration */
232  }
233  } else if (st->codec->bit_rate) {
234  /* No dpds chunk was present (or only an empty one), so estimate
235  * the total duration using the average bits per sample and the
236  * total data length.
237  */
238  st->duration = (size<<3) * st->codec->sample_rate / st->codec->bit_rate;
239  }
240 
241  av_free(dpds_table);
242 
243  return 0;
244 }
245 
247 {
248  int ret, size;
249  int64_t left;
250  AVStream *st;
251  XWMAContext *xwma = s->priv_data;
252 
253  st = s->streams[0];
254 
255  left = xwma->data_end - avio_tell(s->pb);
256  if (left <= 0) {
257  return AVERROR_EOF;
258  }
259 
260  /* read a single block; the default block size is 2230. */
261  size = (st->codec->block_align > 1) ? st->codec->block_align : 2230;
262  size = FFMIN(size, left);
263 
264  ret = av_get_packet(s->pb, pkt, size);
265  if (ret < 0)
266  return ret;
267 
268  pkt->stream_index = 0;
269  return ret;
270 }
271 
273  .name = "xwma",
274  .long_name = NULL_IF_CONFIG_SMALL("Microsoft xWMA"),
275  .priv_data_size = sizeof(XWMAContext),
279 };