FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
xwma.c
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 
25 #include "avformat.h"
26 #include "internal.h"
27 #include "riff.h"
28 
29 /*
30  * Demuxer for xWMA, a Microsoft audio container used by XAudio 2.
31  */
32 
33 typedef struct {
34  int64_t data_end;
35 } XWMAContext;
36 
37 static int xwma_probe(AVProbeData *p)
38 {
39  if (!memcmp(p->buf, "RIFF", 4) && !memcmp(p->buf + 8, "XWMA", 4))
40  return AVPROBE_SCORE_MAX;
41  return 0;
42 }
43 
45 {
46  int64_t size;
47  int ret;
48  uint32_t dpds_table_size = 0;
49  uint32_t *dpds_table = 0;
50  unsigned int tag;
51  AVIOContext *pb = s->pb;
52  AVStream *st;
53  XWMAContext *xwma = s->priv_data;
54  int i;
55 
56  /* The following code is mostly copied from wav.c, with some
57  * minor alterations.
58  */
59 
60  /* check RIFF header */
61  tag = avio_rl32(pb);
62  if (tag != MKTAG('R', 'I', 'F', 'F'))
63  return -1;
64  avio_rl32(pb); /* file size */
65  tag = avio_rl32(pb);
66  if (tag != MKTAG('X', 'W', 'M', 'A'))
67  return -1;
68 
69  /* parse fmt header */
70  tag = avio_rl32(pb);
71  if (tag != MKTAG('f', 'm', 't', ' '))
72  return -1;
73  size = avio_rl32(pb);
74  st = avformat_new_stream(s, NULL);
75  if (!st)
76  return AVERROR(ENOMEM);
77 
78  ret = ff_get_wav_header(pb, st->codec, size);
79  if (ret < 0)
80  return ret;
82 
83  /* All xWMA files I have seen contained WMAv2 data. If there are files
84  * using WMA Pro or some other codec, then we need to figure out the right
85  * extradata for that. Thus, ask the user for feedback, but try to go on
86  * anyway.
87  */
88  if (st->codec->codec_id != AV_CODEC_ID_WMAV2) {
89  avpriv_request_sample(s, "Unexpected codec (tag 0x04%x; id %d)",
90  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  avpriv_request_sample(s, "Unexpected extradata (%d bytes)",
105  st->codec->extradata_size);
106  } else {
107  st->codec->extradata_size = 6;
109  if (!st->codec->extradata)
110  return AVERROR(ENOMEM);
111 
112  /* setup extradata with our experimentally obtained value */
113  st->codec->extradata[4] = 31;
114  }
115  }
116 
117  if (!st->codec->channels) {
118  av_log(s, AV_LOG_WARNING, "Invalid channel count: %d\n",
119  st->codec->channels);
120  return AVERROR_INVALIDDATA;
121  }
122  if (!st->codec->bits_per_coded_sample) {
123  av_log(s, AV_LOG_WARNING, "Invalid bits_per_coded_sample: %d\n",
125  return AVERROR_INVALIDDATA;
126  }
127 
128  /* set the sample rate */
129  avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);
130 
131  /* parse the remaining RIFF chunks */
132  for (;;) {
133  if (pb->eof_reached)
134  return -1;
135  /* read next chunk tag */
136  tag = avio_rl32(pb);
137  size = avio_rl32(pb);
138  if (tag == MKTAG('d', 'a', 't', 'a')) {
139  /* We assume that the data chunk comes last. */
140  break;
141  } else if (tag == MKTAG('d','p','d','s')) {
142  /* Quoting the MSDN xWMA docs on the dpds chunk: "Contains the
143  * decoded packet cumulative data size array, each element is the
144  * number of bytes accumulated after the corresponding xWMA packet
145  * is decoded in order."
146  *
147  * Each packet has size equal to st->codec->block_align, which in
148  * all cases I saw so far was always 2230. Thus, we can use the
149  * dpds data to compute a seeking index.
150  */
151 
152  /* Error out if there is more than one dpds chunk. */
153  if (dpds_table) {
154  av_log(s, AV_LOG_ERROR, "two dpds chunks present\n");
155  return -1;
156  }
157 
158  /* Compute the number of entries in the dpds chunk. */
159  if (size & 3) { /* Size should be divisible by four */
161  "dpds chunk size %"PRId64" not divisible by 4\n", size);
162  }
163  dpds_table_size = size / 4;
164  if (dpds_table_size == 0 || dpds_table_size >= INT_MAX / 4) {
165  av_log(s, AV_LOG_ERROR,
166  "dpds chunk size %"PRId64" invalid\n", size);
167  return -1;
168  }
169 
170  /* Allocate some temporary storage to keep the dpds data around.
171  * for processing later on.
172  */
173  dpds_table = av_malloc(dpds_table_size * sizeof(uint32_t));
174  if (!dpds_table) {
175  return AVERROR(ENOMEM);
176  }
177 
178  for (i = 0; i < dpds_table_size; ++i) {
179  dpds_table[i] = avio_rl32(pb);
180  size -= 4;
181  }
182  }
183  avio_skip(pb, size);
184  }
185 
186  /* Determine overall data length */
187  if (size < 0)
188  return -1;
189  if (!size) {
190  xwma->data_end = INT64_MAX;
191  } else
192  xwma->data_end = avio_tell(pb) + size;
193 
194 
195  if (dpds_table && dpds_table_size) {
196  int64_t cur_pos;
197  const uint32_t bytes_per_sample
198  = (st->codec->channels * st->codec->bits_per_coded_sample) >> 3;
199 
200  /* Estimate the duration from the total number of output bytes. */
201  const uint64_t total_decoded_bytes = dpds_table[dpds_table_size - 1];
202 
203  if (!bytes_per_sample) {
204  av_log(s, AV_LOG_ERROR,
205  "Invalid bits_per_coded_sample %d for %d channels\n",
207  return AVERROR_INVALIDDATA;
208  }
209 
210  st->duration = total_decoded_bytes / bytes_per_sample;
211 
212  /* Use the dpds data to build a seek table. We can only do this after
213  * we know the offset to the data chunk, as we need that to determine
214  * the actual offset to each input block.
215  * Note: If we allowed ourselves to assume that the data chunk always
216  * follows immediately after the dpds block, we could of course guess
217  * the data block's start offset already while reading the dpds chunk.
218  * I decided against that, just in case other chunks ever are
219  * discovered.
220  */
221  cur_pos = avio_tell(pb);
222  for (i = 0; i < dpds_table_size; ++i) {
223  /* From the number of output bytes that would accumulate in the
224  * output buffer after decoding the first (i+1) packets, we compute
225  * an offset / timestamp pair.
226  */
228  cur_pos + (i+1) * st->codec->block_align, /* pos */
229  dpds_table[i] / bytes_per_sample, /* timestamp */
230  st->codec->block_align, /* size */
231  0, /* duration */
233  }
234  } else if (st->codec->bit_rate) {
235  /* No dpds chunk was present (or only an empty one), so estimate
236  * the total duration using the average bits per sample and the
237  * total data length.
238  */
239  st->duration = (size<<3) * st->codec->sample_rate / st->codec->bit_rate;
240  }
241 
242  av_free(dpds_table);
243 
244  return 0;
245 }
246 
248 {
249  int ret, size;
250  int64_t left;
251  AVStream *st;
252  XWMAContext *xwma = s->priv_data;
253 
254  st = s->streams[0];
255 
256  left = xwma->data_end - avio_tell(s->pb);
257  if (left <= 0) {
258  return AVERROR_EOF;
259  }
260 
261  /* read a single block; the default block size is 2230. */
262  size = (st->codec->block_align > 1) ? st->codec->block_align : 2230;
263  size = FFMIN(size, left);
264 
265  ret = av_get_packet(s->pb, pkt, size);
266  if (ret < 0)
267  return ret;
268 
269  pkt->stream_index = 0;
270  return ret;
271 }
272 
274  .name = "xwma",
275  .long_name = NULL_IF_CONFIG_SMALL("Microsoft xWMA"),
276  .priv_data_size = sizeof(XWMAContext),
280 };