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Bug 1388660 - part1 : AudioData::IsAudible() should return false when its data is super small and near to zero. r=jwwang

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When the value of data is too small to be heard, AudioData::IsAudible() should return false so that we won't show the sound indicator for silent media.

In this case, the loudness of reported video is -673 dBFS, it's impossible to be heard.

MozReview-Commit-ID: Ewiko7RpkeX

--HG--
extra : rebase_source : 692e1af570648546deabc3fe4ae4c4b36bf8f356
This commit is contained in:
Alastor Wu 2017-08-17 11:02:11 +08:00
parent 6cea13ecbd
commit d5273690a3
1 changed files with 11 additions and 1 deletions
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12
dom/media/MediaData.cpp
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@ -31,6 +31,16 @@ using media::TimeUnit;
const char* AudioData::sTypeName = "audio";
const char* VideoData::sTypeName = "video";
bool
IsDataLoudnessHearable(const AudioDataValue aData)
{
// We can transfer the digital value to dBFS via following formula. According
// to American SMPTE standard, 0 dBu equals -20 dBFS. In theory 0 dBu is still
// hearable, so we choose a smaller value as our threshold. If the loudness
// is under this threshold, it might not be hearable.
return 20.0f * std::log10(AudioSampleToFloat(aData)) > -100;
}
void
AudioData::EnsureAudioBuffer()
{
@ -66,7 +76,7 @@ AudioData::IsAudible() const
for (uint32_t frame = 0; frame < mFrames; ++frame) {
for (uint32_t channel = 0; channel < mChannels; ++channel) {
if (mAudioData[frame * mChannels + channel] != 0) {
if (IsDataLoudnessHearable(mAudioData[frame * mChannels + channel])) {
return true;
}
}