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mbauman / TrafficSpeed

Using a cell phone video to detect traffic speeds
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Reproducible results #5

Open jehiah opened 8 years ago

jehiah commented 8 years ago

Hi @mbauman First off, this video analysis is amazing.

I'm interested in making the process for doing this analysis more automated as i'd like to try and apply this to some locations in NYC. My first step has been to try to reproduce your findings, familiarize myself with Julia and your processing logic, and i'm happy to say that i've been generally successful.

processedclip

There are generally two issues i've had. One, the video i was able to extract from youtube was 640x360, so calculations where off, and especially the calculations for speed were less accurate because it was lower quality and had compression artifacts. Can you share your original raw video?

The primary code issue i ran into was seek(f, t) didn't work as expected. It seems to be off by a factor of 34. I'm not sure if this is due to something different in the file i exported from youtube, or some other issue. Have you run into anything like that?

mbauman commented 8 years ago

Thanks so much for the note!

I'm afraid I'm away from my computer for the next week, so I probably won't be able to upload the original until after the new year.

I'm not terribly surprised my seek function isn't robust to a different encoding. I'm not familiar with FFMPEG, so I just managed to find something that worked for my file... that's precisely why I didn't push that functionality upstream. I'm probably missing another FFMPEG parameter in the frame rate conversion.

jehiah commented 8 years ago

Upon trying some other export options, I was able to extract 1080p from the youtube video, so i think i'm ok there now. (still hit some oddities w/ the exported file, but i think i have full res now).