EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: eti on September 16, 2022, 02:54:30 am
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Assuming a frame rate of 60fps, and a video of one hour in length, each frame storing a new, unique QR code per frame (corner or side of the frame), how much data could be transmitted from those 216,000 QR codes? I'm sure something could make use of this...
From my rudimentary calculations, I reckon around 1-2Gb of data could be shoehorned in, aside from the video file size.
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Depends on the resolution - the basic QR codes can scale and hold up to some 3kB of data. There are higher density QR codes, such as color coded codes and similar ( https://en.wikipedia.org/wiki/Barcode#Matrix_(2D)_barcodes ). So, 60 fps * 60 seconds * 60 minutes = 216000 frames. With 3kB of data per that's ~650MB. Mind you, the resolution would need to be pretty high to be scanable - the 3kB sized QR codes are fairly big or dense.
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I think the problem you might have is the compression algorithm could make anything but a large QR code difficult to reliably decipher. But if you assume the bitrate is high enough to fit say a 29x29 QR code (a typical size) and reliably decode it on each frame then you can fit 352 bits of data at medium ECC per frame. So 76Mbit, quite a bit less than your estimate of 1-2Gbits.
Edit: but you didn't specify QR code size. Max size is 177x177 for a total bit capacity of 1.2Gbits which meets your range.
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That reminds me on 80ties when we tried to save the data from our ZX and C64 and a like gadgets onto the video tapes.. :D
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Surely it’d be a fool’s errand to do this, given that you could store the QR code’s data in far less data than it would take to store an image of it…
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That reminds me on 80ties when we tried to save the data from our ZX and C64 and a like gadgets onto the video tapes.. :D
Data on audiocassettes was a thing. On videotape? Not with those computers: they had no way to read in anything from videotape. (There were devices to back up PCs to videotape, but those came later.) I mean, you could use a VCR as a glorified audio recorder, but why??
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That reminds me on 80ties when we tried to save the data from our ZX and C64 and a like gadgets onto the video tapes.. :D
Data on audiocassettes was a thing. On videotape? Not with those computers: they had no way to read in anything from videotape. (There were devices to back up PCs to videotape, but those came later.) I mean, you could use a VCR as a glorified audio recorder, but why??
http://members.optusnet.com.au/spacetaxi64/MAIN/VFL-Video-fast-loader-C64.htm (http://members.optusnet.com.au/spacetaxi64/MAIN/VFL-Video-fast-loader-C64.htm)
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Data on audiocassettes was a thing. On videotape? Not with those computers: they had no way to read in anything from videotape. (There were devices to back up PCs to videotape, but those came later.) I mean, you could use a VCR as a glorified audio recorder, but why??
Why use a VCR as an audio recorder - because of non-stop +8 hours of stereo recording/playback.
I still have one of these, and yes - the screen looks a bit like QR code :ø)
https://www.vice.com/en/article/j558k3/how-to-save-files-from-a-pc-to-a-vhs-tape (https://www.vice.com/en/article/j558k3/how-to-save-files-from-a-pc-to-a-vhs-tape)
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Why use a VCR as an audio recorder - because of non-stop +8 hours of stereo recording/playback.
I meant in the context of a C64. It can’t make use of 8 hours of continuous playback. ;)
http://members.optusnet.com.au/spacetaxi64/MAIN/VFL-Video-fast-loader-C64.htm (http://members.optusnet.com.au/spacetaxi64/MAIN/VFL-Video-fast-loader-C64.htm)
Interesting, I stand corrected!
By the 1990 date on that ad, it puts it contemporary to other videotape interfaces (like the backup system I mentioned and TheDane linked to), which is very, very late in the C64’s life!
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https://en.wikipedia.org/wiki/ArVid could store over 4GB on a VHS tape.
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Data on audiocassettes was a thing. On videotape? Not with those computers: they had no way to read in anything from videotape. (There were devices to back up PCs to videotape, but those came later.) I mean, you could use a VCR as a glorified audio recorder, but why??
Why use a VCR as an audio recorder - because of non-stop +8 hours of stereo recording/playback.
I still have one of these, and yes - the screen looks a bit like QR code :ø)
https://www.vice.com/en/article/j558k3/how-to-save-files-from-a-pc-to-a-vhs-tape (https://www.vice.com/en/article/j558k3/how-to-save-files-from-a-pc-to-a-vhs-tape)
I have one of these in a box somewhere. Never used it. Maybe I should crack it out.
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One "just for fun" project I wanted to do is to build a gadget that can record and play back 1080p video on a VHS tape. Easiest would likely be a Raspberry Pi combined with a FPGA or fast microcontroller to handle the data encoding/decoding.
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One "just for fun" project I wanted to do is to build a gadget that can record and play back 1080p video on a VHS tape. Easiest would likely be a Raspberry Pi combined with a FPGA or fast microcontroller to handle the data encoding/decoding.
JVC beat you to it about 20 years ago: https://en.wikipedia.org/wiki/D-VHS
These tapes can store 1080i60 video using MPEG compression. Though the tape is broadly the same as VHS, there's some unmentioned improvements to tape quality which apparently allow this.
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JVC beat you to it about 20 years ago: https://en.wikipedia.org/wiki/D-VHS
These tapes can store 1080i60 video using MPEG compression. Though the tape is broadly the same as VHS, there's some unmentioned improvements to tape quality which apparently allow this.
I was thinking of one that can use standard VHS tape and ideally an unmodified VCR.
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If JVC (the inventor of VHS) couldn’t make it work on standard VHS tape, it’s kinda unlikely someone could do it in their spare time. (Granted, maybe with the very latest video codecs, the bitrate miiiight be low enough to make it work…)
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Regular VHS has a bandwidth of about 3MHz. If you were to do something like QAM you could probably manage 10Mbit/s with error correction and framing. You might be able to go further but you would be pushing the Shannon limit pretty quickly I expect.
10Mbit/s is more than enough for a modern H.265 codec to do 1080p30, and may not even look too bad at 4K (some blocking, but hey, it's VHS!)