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Capture is not lossless. Think about a photocopy machine, every copy loses a small bit of information. Recapturing video output is a similar situation.
by yosito 4y ago
Capture is not lossless. Think about a photocopy machine, every copy loses a small bit of information. Recapturing video output is a similar situation.
- rowanG077 4y agoWhy? Photocopy is obviously lossy since there is a very noisy digital-analog-digital conversion going on. But a capture card is capturing a digital signal. There should be no loss except for video decoding/encoding artifacts.
- donkers 4y agoThe capture itself could be lossless but would be ridiculously huge, re-encoding that to a usable file size will introduce some loss.
- vel0city 4y agoYou're not understanding how lossy compression encoders work. Try recompressing a JPEG a few dozen times. Or take an MP3 and export it from Audacity, open the export, export as MP3 again a dozen times and see what it sounds like. All those artifacts keep getting amplified every time you re-encode until it's practically just the artifacts. Every time you render and recompress you're losing information, it's lossy compression after all. https://youtu.be/icruGcSsPp0 https://youtu.be/icruGcSsPp0
- steve1977 4y agoBut the loss happens during re-encoding, not during capture.
- Hackbraten 4y agoIn practice, that difference doesn’t really matter because almost no one is going to store their captured, already-lossy material in a lossless format.
- porbelm 4y agoIf you know you have to recompress and want to reduce unneccessary artifacts, you do. But beware that uncompressed video in 8 bpc (not HDR) 1080p @ 30 fps is 1,5 Gbps so you'll need 1,3 TB to store your 2-hour capture :)
- vel0city 4y agoLots of the time capture cards are returning a compressed video stream instead of raw frame data, at least for non-professional environments. I don't know too many amateur streamers handling SDI around their house.
- icelancer 4y agoThought for sure it was going to be the legendary Hank Hill JPEG meme: https://www.youtube.com/watch?v=QEzhxP-pdos https://www.youtube.com/watch?v=QEzhxP-pdos
- vel0city 4y agoI just want a picture of a got-dang hot dog! Truly a classic.
- botanical 4y agoBut JPEG purposely discards information to save space. A digital stream is copied directly, only a codec would subject it losing information
- jenadine 4y agoBut if you want to share it or store it, it is not practical to keep the raw data. You will have to re-encode.
- happymellon 4y agoLike the codec used to get the stream from Netflix to you, to be decompressed for the capture card (so lossless capture of a lossy source) and then back through x264/265 so lossy compression on a lossy compression. Just because there is a capture card in the middle doesn't stop it going through multiple lossy steps.
- yosito 4y ago> except for video decoding/encoding artifacts Which is... lossy