AV delay measurement and correction via signature curves
View Patent ↗Embodiments of the present invention provide systems and methods for non-invasive, “in-service” AV delay detection and correction. These systems and methods do not modify the audio signal or the video signal, nor do they rely on any metadata to be carried with the audio signal or the video signal via the distribution path. Instead, agents located at various points along the distribution path generate very small signature curves for the audio signal and the video signal and distribute them to a manager via a separate data path other than the distribution path. The manager calculates a measured AV delay caused by the distribution path based on these signature curves, and then optionally corrects the measured AV delay by adjusting an in-line delay in the distribution path.
1. A device comprising:
an input for receiving an audio/video (AV) program at a point along a distribution path, the AV program having an audio signal and a video signal; and
a processor for processing the audio signal to generate an audio signature curve, and for processing the video signal to generate a video signature curve;
wherein the processor comprises:
a first band-pass filter for filtering a left channel of the audio signal to produce a filtered left channel;
a first envelope detector for detecting an envelope of the filtered left channel;
a second band-pass filter for filtering a right channel of the audio signal to produce a filtered right channel;
a second envelope detector for detecting an envelope of the filtered right channel;
a summer for summing the envelope of the filtered left channel and the envelope of the envelope of the filtered right channel to produce a sum;
a low-pass filter for filtering the sum to produce a filtered sum; and
a sampler for sampling the filtered sum at the frame or field rate to produce the audio signature curve.
2. A device as in claim 1 further comprising an output for distributing the audio signature curve and the video signature curve via a separate data path other than the distribution path.
3. A device as in claim 1 wherein the processor comprises means for generating the video signature curve based on a co-variance of adjacent frames of the video signal.
4. A device as in claim 1 wherein the processor comprises means for generating the video signature curve based on a co-variance of adjacent frame differences of the video signal.
5. A method comprising the steps of:
receiving an audio/video (AV) program at a point along a distribution path, the AV program having an audio signal and a video signal; and
generating an audio signature curve based on the audio signal, and a video signature curve based on the video signal;
wherein the audio signature curve is generated by:
filtering a left channel of the audio signal to produce a filtered left channel;
detecting an envelope of the filtered left channel;
filtering a right channel of the audio signal to produce a filtered right channel;
detecting an envelope of the filtered right channel;
summing the envelope of the filtered left channel and the envelope of the envelope of the filtered right channel to produce a sum;
filtering the sum to produce a filtered sum; and
sampling the filtered sum at the frame or field rate to produce the audio signature curve.
6. A method as in claim 5 further comprising the step of distributing the audio signature curve and the video signature curve via a separate data path other than the distribution path.
7. A method as in claim 5 wherein the video signature curve is generated based on a co-variance of adjacent frames of the video signal.
8. A method as in claim 5 wherein the video signature curve is generated based on a co-variance of adjacent frame differences of the video signal.