Pretty cool indeed. A question though: how much of a need is there for a service like this? Beyond the more mainstream artists and festivals, most of the artists whose shows I've seen have typically had more respectful audience members who didnt put recording with their cellphones ahead of enjoying the show.
Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
81–90 of 132 posts
Re: Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
#82to me, it looks amazing
some techie questions, how does it work? how do you get to know which videos are actually part of a specific event? how do you match the video with the actual song?
Re: Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
#83Earlier quoted context omitted.
This seems unlikely to be possible. If you haven't captured any frequencies above 15kHz (which an average cell phone mic is unlikely to do), no amount of averaging, filtering, or combining will get them back. There will also be a considerable amount of distortion, since concerts tend to be so loud that even one's ears are distorting. Good luck separating physical distortion in the mic, limiter distortion in the analo…
If you haven't captured any frequencies above 15kHz (which an average cell phone mic is unlikely to do), no amount of averaging, filtering, or combining will get them back. I think this is technically not quite true. If two cell phones right next to each other are both sampling at 15kHz, in the best case you could combine their samples to get an equivalent sampling of 30 kHz. (Best case meaning phone 1 samples exactl…
Only if the two phones are under-sampling the signal.
Chances are that there is a low pass filter in front of the phone's ADC, blocking signals above the Nyquist limit from reaching the sampler. Assuming brick wall filters (ie perfect cutoff), combining the signals will reduce variance (noise) but not give any information on frequencies above the cutoff frequency of the filter.
Brick wall filters don't exist though. What you might see is a miniscule amount of signal in the filter's stop band. Combining the signal from many many phones might reduce the variable enough to give useful information for frequencies a tiny bit above the cutoff frequency.
A cool project would be to gather the audio from every networked microphone in an area (mobile phones, laptops, ...) and use beam-forming techniques to reconstruct the sound pressure field as a function of position. My guess is that the system would be sensitive enough that it could do amazing things like capture conversations though walls or from long distances.
Re: Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
#84This is really awesome. I hope you don't have any issues with copyright though. Best of luck with the project!
Re: Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
#85Earlier quoted context omitted.
If you haven't captured any frequencies above 15kHz (which an average cell phone mic is unlikely to do), no amount of averaging, filtering, or combining will get them back. I think this is technically not quite true. If two cell phones right next to each other are both sampling at 15kHz, in the best case you could combine their samples to get an equivalent sampling of 30 kHz. (Best case meaning phone 1 samples exactl…
This is unfortunately so unlikely to as to be practically impossible (currently!). If the microphones, ADCs etc on both phones are incapable of capturing frequencies of above e.g. 15Khz below a certain range, combining those signals definitely won't bring you any closer to the original signal. You may be able to cancel out a fair bit of noise given enough processing but you won't get back what hasn't been originally…
Sorry to be off topic here... but this is why I don't understand HN sometimes - the post above isn't nasty, augmentative, hurtful or 'bad' in any way, but instead of people responding to the poster they've downvoted him.
Isn't downvoting for removing bad content, not trying to silence someone you don't agree with?
Thoughts/comments?
(edit - post is no longer showing as greyed out/downvoted - but still, any comments?)
Re: Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
#86Earlier quoted context omitted.
That is just so much harder; though I haven't looked at the website yet, seems to be overwhelmed right now. Besides, I would want one consistent audio signal instead of one that varies in noise, volume, whatever. Video from different sources is alright though, since we are used to switching scenes and cameras all the time.
The idea I'm talking about should provide a single consistent audio signal. I know nothing about audio processing, but it seems like it should be possible to take multiple bad audio signals and combine them into one signal that's better than any constituent audio source. Perhaps one audio source captured low frequencies well, while another captured higher frequencies better.
>take multiple bad audio signals and combine them into one signal that's better
The problem eventually comes down to the fact that "better" is subjective. We're in the murky realm of art here. Should your algorithm keep that fret noise or the squeaking of a vocalist's intake of breath? Are they "noise," or are they part of the performance?
>I know nothing about audio processing
Not wishing to be rude, but this much is very evident. Recording engineers position their microphones with millimetre precision in order to combat phase issues, and that is in an ideal studio scenario. Doing what you suggest is basically impossible.
Maybe I'm overstating it, you could probably do something and it'd be a nice bit of research, but you wouldn't get useful results in the way that you're imagining.
Re: Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
#87Earlier quoted context omitted.
The idea I'm talking about should provide a single consistent audio signal. I know nothing about audio processing, but it seems like it should be possible to take multiple bad audio signals and combine them into one signal that's better than any constituent audio source. Perhaps one audio source captured low frequencies well, while another captured higher frequencies better.
If both channels have a similar spike at the same frequency at the same time, it is probably part of the signal (not noise), so combine those, and dampen all others. This would cover your case, if the other channel had enough of the low/hi freq of the other to relate them. I reckon Shannon looked at exactly this in developing Information Theory (for telephone signals on flaky lines), and it's probably all textbook st…
>at the same time
The thing is, sound doesn't travel all that fast when you consider the wavelengths of vocal-range soundwaves. Those spikes are not going to arrive at the same time on the different phones.
As ever with DSP, phase problems will be the ruin of you.
Re: Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
#88My out loud comment when I tried it was "Holy shit this is genius if it works".
Re: Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
#89Cool concept, fairly good execution.
I think I would advise not to just focus on concerts, but potentially other mass events, e.g. sporting events.
I guess you're using the audio stream to do some form of sync / time stamp though, so that may limit potential uses.
Re: Show HN: Entire concerts algorithmically "reconstructed" from YouTube videos
#90Earlier quoted context omitted.
If both channels have a similar spike at the same frequency at the same time, it is probably part of the signal (not noise), so combine those, and dampen all others. This would cover your case, if the other channel had enough of the low/hi freq of the other to relate them. I reckon Shannon looked at exactly this in developing Information Theory (for telephone signals on flaky lines), and it's probably all textbook st…
>at the same time The thing is, sound doesn't travel all that fast when you consider the wavelengths of vocal-range soundwaves. Those spikes are not going to arrive at the same time on the different phones. As ever with DSP, phase problems will be the ruin of you.
nice point, but they'd synchronize with an offset. I doubt absolute time would be used to synchronize the videos anyway; they'd be matched by content.
Or do you mean that different frequencies will travel at different speeds, enough to make (e.g.) high and low frequencies arrive at different times? Whoa, apparently it does (http://en.wikipedia.org/wiki/Speed_of_sound#Effect_of_freque...) but seems to be a small effect.