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#Actualcr88192

Posted 20 March 2013 - 06:12 PM

actually, perception is fairly lax when it comes to audio/visual sync delays.
IME, much under about 100-200ms and it isn't really all that noticeable.

more so, getting much under around 50-100ms may be itself difficult, largely due to the granularity introduced by things like the game-tick and similar (which is often lower than the raw framerate, where at 60fps, the frame-time is around 17ms, but the game-tick may only be at 10 or 16Hz, or 62-100ms).

there may also be the issue of keeping the audio mixer all that precisely aligned with the sound-output from the audio hardware, so typically a tolerance is used here, with the mixer re-aligning if this drifts much outside 100ms or so (much past 100-200ms and the audio and visuals start to get noticeably out of sync).

however, we don't want to re-align too aggressively, as this will typically introduce audible defects, which are often much more obvious. for example, we may need to occasionally pad-out or skip forwards to get things back in sync, but simply jumping will typically result in an obvious "pop" (and padding things out with silence isn't much better), so it is usually necessary to blend over a skip (via interpolation), and insert some "filler" (such as previously mixed samples) for padding things out (with blending at both ends). even then, it is still often noticeable (but, at least the loud/obvious pop can be avoided).


ADD/IME: actually, another observation is that while nearest and linear interpolation (such as in trilinear filtering) often work ok for graphics, nearest and linear interpolation sound poor for audio mixing, so generally a person needs cubic interpolation for upsampling and resampling. to more effectively support arbitrary resampling, such as in Doppler shifts, a stragegy resembling mip-mapping can be used, where the sample is interpolated for each mip-level, and then interpolated between mip-levels.

#3cr88192

Posted 20 March 2013 - 06:06 PM

actually, perception is fairly lax when it comes to audio/visual sync delays.
IME, much under about 100-200ms and it isn't really all that noticeable.

more so, getting much under around 50-100ms may be itself difficult, largely due to the granularity introduced by things like the game-tick and similar (which is often lower than the raw framerate, where at 60fps, the frame-time is around 17ms, but the game-tick may only be at 10 or 16Hz, or 62-100ms).

there may also be the issue of keeping the audio mixer all that precisely aligned with the sound-output from the audio hardware, so typically a tolerance is used here, with the mixer re-aligning if this drifts much outside 100ms or so (much past 100-200ms and the audio and visuals start to get noticeably out of sync).

however, we don't want to re-align too aggressively, as this will typically introduce audible defects, which are often much more obvious. for example, we may need to occasionally pad-out or skip forwards to get things back in sync, but simply jumping will typically result in an obvious "pop" (and padding things out with silence isn't much better), so it is usually necessary to blend over a skip (via interpolation), and insert some "filler" (such as previously mixed samples) for padding things out (with blending at both ends). even then, it is still often noticeable (but, at least the loud/obvious pop can be avoided).


ADD/IME: actually, another observation is that while nearest and linear interpolation (such as in trilinear filtering) often work ok for graphics, nearest and linear interpolation sound poor for audio mixing, so generally a person needs cubic interpolation for upsampling, and bicubic for resampling. to more effectively support arbitrary resampling, such as in Doppler shifts, a stragegy resembling mip-mapping can be used, where the sample is interpolated for each mip-level, and then interpolated between mip-levels.

#2cr88192

Posted 20 March 2013 - 05:20 PM

actually, perception is fairly lax when it comes to audio/visual sync delays.
IME, much under about 100-200ms and it isn't really all that noticeable.

more so, getting much under around 50-100ms may be itself difficult, largely due to the granularity introduced by things like the game-tick and similar (which is often lower than the raw framerate, where at 60fps, the frame-time is around 17ms, but the game-tick may only be at 10 or 16Hz, or 62-100ms).

there may also be the issue of keeping the audio mixer all that precisely aligned with the sound-output from the audio hardware, so typically a tolerance is used here, with the mixer re-aligning if this drifts much outside 100ms or so (much past 100-200ms and the audio and visuals start to get noticeably out of sync).

however, we don't want to re-align too aggressively, as this will typically introduce audible defects, which are often much more obvious. for example, we may need to occasionally pad-out or skip forwards to get things back in sync, but simply jumping will typically result in an obvious "pop" (and padding things out with silence isn't much better), so it is usually necessary to blend over a skip (via interpolation), and insert some "filler" (such as previously mixed samples) for padding things out (with blending at both ends). even then, it is still often noticeable (but, at least the loud/obvious pop can be avoided).

#1cr88192

Posted 20 March 2013 - 05:00 PM

actually, perception is fairly lax when it comes to audio/visual delays.
IME, much under about 100-200ms and it isn't really all that noticeable.

more so, getting much under around 50-100ms may be itself difficult, largely due to the granularity introduced by things like the game-tick and similar (which is often lower than the raw framerate, where at 60fps, the frame-time is around 17ms, but the game-tick may only be at 10 or 16Hz).

there may also be the issue of keeping the audio mixer all that precisely aligned with the sound-output from the audio hardware, so typically a tolerance is used here, with the mixer re-aligning if this drifts much outside 100ms or so (much past 100-200ms and the audio and visuals start to get noticeably out of sync).

however, we don't want to re-align too aggressively, as this will typically introduce audible defects, which are often much more obvious. for example, we may need to occasionally pad-out or skip forwards to get things back in sync, but simply jumping will typically result in an obvious "pop", so it is usually necessary to blend over a skip (via interpolation), and insert some "filler" (such as previously mixed samples) for padding things out (with blending at both ends). even then, it is still often noticeable (but, at least the loud/obvious pop can be avoided).

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