Rewrite resampler #166
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Rewrite resampler #166
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MarkKremer
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The original length of pts made sense because when wantPos is a decimal position like 3.5, you want the window for quality 1 to contain positions 3 and 4. Having a window of 1 more doesn't make sense for that. My previous reasoning for increasing the window size was arguing from the point of wantPosition always being an integer value, which isn't the case.
Two bugs: - SetRatio() could cause out of range panic when the ratio was sufficiently big. This happens when the newly calculated position was casted to an int. This caused the value to be rounded down. If difference times the ratio was bigger than the buffer, the calculated wantPos could be a negative index in buf1. - When the ratio is sufficiently big, the Stream function may not only need to fill the buffers with new data once, but multiple times. The if statement has been replaced with a for loop, so the check is executed until the desired samples are reached.
dusk125
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Jul 30, 2024
dusk125
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Jul 31, 2024
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Fix for #20
Rewritten the
Resamplerto make the code easier to read & fix some bugs:When the source streamer didn't conform the
Streamerinterface by returning a drained signal & then returning samples again, the internal buffer could be resized and unsuitable to do the job causing an out of range panic. The new resampler keeps track of the end of the stream. When the end is reached, it will simply stay in a drained state.SetRatiowith a big enough ratio could cause an out of range panic. This was because during the calculation of the newpos, the result was cast to an int. If the ratio was so big that this rounding down caused a different of more than the buffer size, the buffer would be indexed with a negative value. I don't expect any reasonable application to run into this error, but it's nice to not get panics when playing around with the speedy-player example. That said, I've added some limits to the values that can be selected in that example.posis now afloat64. I expect this to carry enough precision for most use-cases. Say you have a resample ratio of 1/6 (from 8000 to 48000), 48000 samples per seconds, 86400 seconds in a day, 365 days in a year, the number of unique values would be6*48000*86400*365 = 9.082368×10^12.float64has enough precision to hold a bit less than 16 decimal digits so even though I'm not entirely sure how much we need, there is still a bunch of wiggle room.SetRatiobeing more precise is probably good for theDopplerstreamer. Less samples will be skipped over.Streamfetches new samples from the source streamer to fill the buffer when it detects that the samples needed for the interpolation are after the currently loaded buffers. However, when the ratio is larger than the buffer size, the needed samples could be more than one buffer away. I've replaced theifstatement with aforloop so it keeps streaming samples until it reaches the right index. This solves another out of range panic.I've added a fuzz test to confirm weird resample ratios don't cause panics anymore.
It seems that the doppler example is now easier to crash. But the
Dopplerstreamer is experimental and was giving the resampler invalid ratios. It probably needs a rewrite as well, but that something for another day.