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 "exceptions.h"
24 #include "resampler.h"
30 using std::stringstream;
36 using boost::optional;
37 using boost::shared_ptr;
39 AudioDecoder::AudioDecoder (shared_ptr<const AudioContent> content)
40 : _audio_content (content)
42 if (content->resampled_audio_frame_rate() != content->audio_frame_rate() && content->audio_channels ()) {
43 _resampler.reset (new Resampler (content->audio_frame_rate(), content->resampled_audio_frame_rate(), content->audio_channels ()));
46 reset_decoded_audio ();
50 AudioDecoder::reset_decoded_audio ()
52 _decoded_audio = ContentAudio (shared_ptr<AudioBuffers> (new AudioBuffers (_audio_content->audio_channels(), 0)), 0);
55 shared_ptr<ContentAudio>
56 AudioDecoder::get_audio (AudioFrame frame, AudioFrame length, bool accurate)
58 shared_ptr<ContentAudio> dec;
60 AudioFrame const end = frame + length - 1;
62 if (frame < _decoded_audio.frame || end > (_decoded_audio.frame + length * 4)) {
63 /* Either we have no decoded data, or what we do have is a long way from what we want: seek */
64 seek (ContentTime::from_frames (frame, _audio_content->audio_frame_rate()), accurate);
67 /* Offset of the data that we want from the start of _decoded_audio.audio
68 (to be set up shortly)
70 AudioFrame decoded_offset = 0;
72 /* Now enough pass() calls will either:
73 * (a) give us what we want, or
74 * (b) hit the end of the decoder.
76 * If we are being accurate, we want the right frames,
77 * otherwise any frames will do.
80 /* Keep stuffing data into _decoded_audio until we have enough data, or the subclass does not want to give us any more */
81 while (!pass() && (_decoded_audio.frame > frame || (_decoded_audio.frame + _decoded_audio.audio->frames()) < end)) {}
82 decoded_offset = frame - _decoded_audio.frame;
84 while (!pass() && _decoded_audio.audio->frames() < length) {}
85 /* Use decoded_offset of 0, as we don't really care what frames we return */
88 /* The amount of data available in _decoded_audio.audio starting from `frame'. This could be -ve
89 if pass() returned true before we got enough data.
91 AudioFrame const available = _decoded_audio.audio->frames() - decoded_offset;
93 /* We will return either that, or the requested amount, whichever is smaller */
94 AudioFrame const to_return = max ((AudioFrame) 0, min (available, length));
96 /* Copy our data to the output */
97 shared_ptr<AudioBuffers> out (new AudioBuffers (_decoded_audio.audio->channels(), to_return));
98 out->copy_from (_decoded_audio.audio.get(), to_return, decoded_offset, 0);
100 AudioFrame const remaining = max ((AudioFrame) 0, available - to_return);
102 /* Clean up decoded; first, move the data after what we just returned to the start of the buffer */
103 _decoded_audio.audio->move (decoded_offset + to_return, 0, remaining);
104 /* And set up the number of frames we have left */
105 _decoded_audio.audio->set_frames (remaining);
106 /* Also bump where those frames are in terms of the content */
107 _decoded_audio.frame += decoded_offset + to_return;
109 return shared_ptr<ContentAudio> (new ContentAudio (out, frame));
112 /** Called by subclasses when audio data is ready.
114 * Audio timestamping is made hard by many factors, but perhaps the most entertaining is resampling.
115 * We have to assume that we are feeding continuous data into the resampler, and so we get continuous
116 * data out. Hence we do the timestamping here, post-resampler, just by counting samples.
118 * The time is passed in here so that after a seek we can set up our _audio_position. The
119 * time is ignored once this has been done.
122 AudioDecoder::audio (shared_ptr<const AudioBuffers> data, ContentTime time)
125 data = _resampler->run (data);
128 AudioFrame const frame_rate = _audio_content->resampled_audio_frame_rate ();
130 if (_seek_reference) {
131 /* We've had an accurate seek and now we're seeing some data */
132 ContentTime const delta = time - _seek_reference.get ();
133 AudioFrame const delta_frames = delta.frames (frame_rate);
134 if (delta_frames > 0) {
135 /* This data comes after the seek time. Pad the data with some silence. */
136 shared_ptr<AudioBuffers> padded (new AudioBuffers (data->channels(), data->frames() + delta_frames));
137 padded->make_silent ();
138 padded->copy_from (data.get(), data->frames(), 0, delta_frames);
141 } else if (delta_frames < 0) {
142 /* This data comes before the seek time. Throw some data away */
143 AudioFrame const to_discard = min (-delta_frames, static_cast<AudioFrame> (data->frames()));
144 AudioFrame const to_keep = data->frames() - to_discard;
146 /* We have to throw all this data away, so keep _seek_reference and
147 try again next time some data arrives.
151 shared_ptr<AudioBuffers> trimmed (new AudioBuffers (data->channels(), to_keep));
152 trimmed->copy_from (data.get(), to_keep, to_discard, 0);
154 time += ContentTime::from_frames (to_discard, frame_rate);
156 _seek_reference = optional<ContentTime> ();
159 if (!_audio_position) {
160 _audio_position = time.frames (frame_rate);
163 assert (_audio_position.get() >= (_decoded_audio.frame + _decoded_audio.audio->frames()));
165 /* Resize _decoded_audio to fit the new data */
167 if (_decoded_audio.audio->frames() == 0) {
168 /* There's nothing in there, so just store the new data */
169 new_size = data->frames ();
170 _decoded_audio.frame = _audio_position.get ();
172 /* Otherwise we need to extend _decoded_audio to include the new stuff */
173 new_size = _audio_position.get() + data->frames() - _decoded_audio.frame;
176 _decoded_audio.audio->ensure_size (new_size);
177 _decoded_audio.audio->set_frames (new_size);
179 /* Copy new data in */
180 _decoded_audio.audio->copy_from (data.get(), data->frames(), 0, _audio_position.get() - _decoded_audio.frame);
181 _audio_position = _audio_position.get() + data->frames ();
186 AudioDecoder::flush ()
193 shared_ptr<const AudioBuffers> b = _resampler->flush ();
195 _pending.push_back (shared_ptr<DecodedAudio> (new DecodedAudio (b, _audio_position.get ())));
196 _audio_position = _audio_position.get() + b->frames ();
202 AudioDecoder::seek (ContentTime t, bool accurate)
204 _audio_position.reset ();
205 reset_decoded_audio ();