2 Copyright (C) 2012-2014 Carl Hetherington <cth@carlh.net>
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 #include "audio_decoder.h"
21 #include "audio_buffers.h"
22 #include "audio_processor.h"
23 #include "resampler.h"
34 using boost::optional;
35 using boost::shared_ptr;
37 AudioDecoder::AudioDecoder (shared_ptr<const AudioContent> content)
38 : _audio_content (content)
40 if (content->resampled_audio_frame_rate() != content->audio_frame_rate() && content->audio_channels ()) {
41 _resampler.reset (new Resampler (content->audio_frame_rate(), content->resampled_audio_frame_rate(), content->audio_channels ()));
44 if (content->audio_processor ()) {
45 _processor = content->audio_processor()->clone (content->resampled_audio_frame_rate ());
48 reset_decoded_audio ();
52 AudioDecoder::reset_decoded_audio ()
54 _decoded_audio = ContentAudio (shared_ptr<AudioBuffers> (new AudioBuffers (_audio_content->processed_audio_channels(), 0)), 0);
57 shared_ptr<ContentAudio>
58 AudioDecoder::get_audio (AudioFrame frame, AudioFrame length, bool accurate)
60 shared_ptr<ContentAudio> dec;
62 AudioFrame const end = frame + length - 1;
64 if (frame < _decoded_audio.frame || end > (_decoded_audio.frame + length * 4)) {
65 /* Either we have no decoded data, or what we do have is a long way from what we want: seek */
66 seek (ContentTime::from_frames (frame, _audio_content->audio_frame_rate()), accurate);
69 /* Offset of the data that we want from the start of _decoded_audio.audio
70 (to be set up shortly)
72 AudioFrame decoded_offset = 0;
74 /* Now enough pass() calls will either:
75 * (a) give us what we want, or
76 * (b) hit the end of the decoder.
78 * If we are being accurate, we want the right frames,
79 * otherwise any frames will do.
82 /* Keep stuffing data into _decoded_audio until we have enough data, or the subclass does not want to give us any more */
83 while ((_decoded_audio.frame > frame || (_decoded_audio.frame + _decoded_audio.audio->frames()) < end) && !pass ()) {}
84 decoded_offset = frame - _decoded_audio.frame;
86 while (_decoded_audio.audio->frames() < length && !pass ()) {}
87 /* Use decoded_offset of 0, as we don't really care what frames we return */
90 /* The amount of data available in _decoded_audio.audio starting from `frame'. This could be -ve
91 if pass() returned true before we got enough data.
93 AudioFrame const available = _decoded_audio.audio->frames() - decoded_offset;
95 /* We will return either that, or the requested amount, whichever is smaller */
96 AudioFrame const to_return = max ((AudioFrame) 0, min (available, length));
98 /* Copy our data to the output */
99 shared_ptr<AudioBuffers> out (new AudioBuffers (_decoded_audio.audio->channels(), to_return));
100 out->copy_from (_decoded_audio.audio.get(), to_return, decoded_offset, 0);
102 AudioFrame const remaining = max ((AudioFrame) 0, available - to_return);
104 /* Clean up decoded; first, move the data after what we just returned to the start of the buffer */
105 _decoded_audio.audio->move (decoded_offset + to_return, 0, remaining);
106 /* And set up the number of frames we have left */
107 _decoded_audio.audio->set_frames (remaining);
108 /* Also bump where those frames are in terms of the content */
109 _decoded_audio.frame += decoded_offset + to_return;
111 return shared_ptr<ContentAudio> (new ContentAudio (out, frame));
114 /** Called by subclasses when audio data is ready.
116 * Audio timestamping is made hard by many factors, but perhaps the most entertaining is resampling.
117 * We have to assume that we are feeding continuous data into the resampler, and so we get continuous
118 * data out. Hence we do the timestamping here, post-resampler, just by counting samples.
120 * The time is passed in here so that after a seek we can set up our _audio_position. The
121 * time is ignored once this has been done.
124 AudioDecoder::audio (shared_ptr<const AudioBuffers> data, ContentTime time)
127 data = _resampler->run (data);
131 data = _processor->run (data);
134 AudioFrame const frame_rate = _audio_content->resampled_audio_frame_rate ();
136 if (_seek_reference) {
137 /* We've had an accurate seek and now we're seeing some data */
138 ContentTime const delta = time - _seek_reference.get ();
139 AudioFrame const delta_frames = delta.frames (frame_rate);
140 if (delta_frames > 0) {
141 /* This data comes after the seek time. Pad the data with some silence. */
142 shared_ptr<AudioBuffers> padded (new AudioBuffers (data->channels(), data->frames() + delta_frames));
143 padded->make_silent ();
144 padded->copy_from (data.get(), data->frames(), 0, delta_frames);
147 } else if (delta_frames < 0) {
148 /* This data comes before the seek time. Throw some data away */
149 AudioFrame const to_discard = min (-delta_frames, static_cast<AudioFrame> (data->frames()));
150 AudioFrame const to_keep = data->frames() - to_discard;
152 /* We have to throw all this data away, so keep _seek_reference and
153 try again next time some data arrives.
157 shared_ptr<AudioBuffers> trimmed (new AudioBuffers (data->channels(), to_keep));
158 trimmed->copy_from (data.get(), to_keep, to_discard, 0);
160 time += ContentTime::from_frames (to_discard, frame_rate);
162 _seek_reference = optional<ContentTime> ();
165 if (!_audio_position) {
166 _audio_position = time.frames (frame_rate);
169 assert (_audio_position.get() >= (_decoded_audio.frame + _decoded_audio.audio->frames()));
175 AudioDecoder::add (shared_ptr<const AudioBuffers> data)
177 if (!_audio_position) {
178 /* This should only happen when there is a seek followed by a flush, but
179 we need to cope with it.
184 /* Resize _decoded_audio to fit the new data */
186 if (_decoded_audio.audio->frames() == 0) {
187 /* There's nothing in there, so just store the new data */
188 new_size = data->frames ();
189 _decoded_audio.frame = _audio_position.get ();
191 /* Otherwise we need to extend _decoded_audio to include the new stuff */
192 new_size = _audio_position.get() + data->frames() - _decoded_audio.frame;
195 _decoded_audio.audio->ensure_size (new_size);
196 _decoded_audio.audio->set_frames (new_size);
198 /* Copy new data in */
199 _decoded_audio.audio->copy_from (data.get(), data->frames(), 0, _audio_position.get() - _decoded_audio.frame);
200 _audio_position = _audio_position.get() + data->frames ();
202 /* Limit the amount of data we keep in case nobody is asking for it */
203 int const max_frames = _audio_content->resampled_audio_frame_rate () * 10;
204 if (_decoded_audio.audio->frames() > max_frames) {
205 int const to_remove = _decoded_audio.audio->frames() - max_frames;
206 _decoded_audio.frame += to_remove;
207 _decoded_audio.audio->move (to_remove, 0, max_frames);
208 _decoded_audio.audio->set_frames (max_frames);
213 AudioDecoder::flush ()
219 shared_ptr<const AudioBuffers> b = _resampler->flush ();
226 AudioDecoder::seek (ContentTime t, bool accurate)
228 _audio_position.reset ();
229 reset_decoded_audio ();
234 _processor->flush ();