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NetEq: Fix a bug in expand_rate and speech_expand_rate calculation

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After a Merge operation, the statistics for number of samples
generated using Expand must be corrected, and the correction can in
fact be negative. However, a bug was introduced in
https://codereview.webrtc.org/1230503003 which uses a size_t to
represent the correction, which leads to wrap-around of the negative
value. This is not a problem in itself, since this value is added to
another size_t, with the effect that the desired subtraction happens
anyway.

The actual problem arises if the statistics are polled/reset before a
subtraction happens -- that is, between an Expand and a Merge
operation. This will lead to an actual wrap-around of the stats value,
and large expand_rate (16384) is reported.

BUG=webrtc:7554

Review-Url: https://codereview.webrtc.org/2859483005
Cr-Commit-Position: refs/heads/master@{#18029}
This commit is contained in:
henrik.lundin
2017-05-05 05:04:16 -07:00
committed by Commit bot
parent 2a28035627
commit 2979f55f95
5 changed files with 45 additions and 14 deletions
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10
webrtc/modules/audio_coding/neteq/neteq_impl.cc
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@ -1600,16 +1600,18 @@ void NetEqImpl::DoMerge(int16_t* decoded_buffer, size_t decoded_length,
size_t new_length = merge_->Process(decoded_buffer, decoded_length,
mute_factor_array_.get(),
algorithm_buffer_.get());
size_t expand_length_correction = new_length -
decoded_length / algorithm_buffer_->Channels();
// Correction can be negative.
int expand_length_correction =
rtc::dchecked_cast<int>(new_length) -
rtc::dchecked_cast<int>(decoded_length / algorithm_buffer_->Channels());
// Update in-call and post-call statistics.
if (expand_->MuteFactor(0) == 0) {
// Expand generates only noise.
stats_.ExpandedNoiseSamples(expand_length_correction);
stats_.ExpandedNoiseSamplesCorrection(expand_length_correction);
} else {
// Expansion generates more than only noise.
stats_.ExpandedVoiceSamples(expand_length_correction);
stats_.ExpandedVoiceSamplesCorrection(expand_length_correction);
}
last_mode_ = kModeMerge;