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LibAudio: Seek accurately to the target frame in the FLAC loader

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Instead of using a seek tolerance value to get close enough to the
target, we can skip frames forward until we pass the target, then seek
back to the previous frame. That puts us in a position to immediately
decode the frame containing the target sample.
This commit is contained in:
Zaggy1024 2023-07-05 02:41:12 -05:00 • committed by Linus Groh
parent f2d9280342
commit 9d5819e9e2
1 changed files with 6 additions and 3 deletions
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9
Userland/Libraries/LibAudio/FlacLoader.cpp
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@ -285,7 +285,6 @@ MaybeLoaderError FlacLoaderPlugin::seek(int int_sample_index)
return {};
auto maybe_target_seekpoint = m_seektable.seek_point_before(sample_index);
auto const seek_tolerance = (seek_tolerance_ms * m_sample_rate) / 1000;
// No seektable or no fitting entry: Perform normal forward read
if (!maybe_target_seekpoint.has_value()) {
if (sample_index < m_loaded_samples) {
@ -310,11 +309,15 @@ MaybeLoaderError FlacLoaderPlugin::seek(int int_sample_index)
}
}
// Skip frames until we're within the seek tolerance.
while (sample_index - m_loaded_samples > seek_tolerance) {
// Skip frames until we're just before the target sample.
VERIFY(m_loaded_samples <= sample_index);
size_t frame_start_location;
while (m_loaded_samples <= sample_index) {
frame_start_location = TRY(m_stream->tell());
(void)TRY(next_frame());
m_loaded_samples += m_current_frame->sample_count;
}
TRY(m_stream->seek(frame_start_location, SeekMode::SetPosition));
return {};
}