10 ms·

Interlacing, Deinterlacing, and Everything in Between

55 points by MindGods 5y ago

msla 5y ago
> We hit a strange truth about analog monochrome television: the vertical resolution is strictly limited: it’s the number of lines you draw. But the horizontal resolution, the resolution within each line, is basically infinite; it’s a purely analog signal. The only thing that holds it back is how quickly the electronics in your television can keep up. No, it's strictly limited by the bandwidth of the television signal. You could have infinitely responsive circuitry but you'd still have horizontal resolution limited by the bandwidth of the video portion of the broadcast TV signal. About all you can say is that analog TV does not have pixels. Anyway, here's a video (part of a series) on how analog TV works: https://www.youtube.com/watch?v=l4UgZBs7ZGo https://www.youtube.com/watch?v=l4UgZBs7ZGo Full playlist: https://www.youtube.com/playlist?list=PLv0jwu7G_DFUGEfwEl0uWduXGcRbT7Ran https://www.youtube.com/playlist?list=PLv0jwu7G_DFUGEfwEl0uW...
- whatshisface 5y ago
  >About all you can say is that analog TV does not have pixels. Color analog TVs have discrete patches of different phosphors.
  - TazeTSchnitzel 5y ago
    Those aren't really pixels though: the signal can (and does) vary within them.
chrisseaton 5y ago
What does industry do about interlacing? I understand many TV shows were recorded and mastered on video with interlacing. When they re-release the TV shows for example for Netflix - what are they currently doing?
- cogman10 5y ago
  Last I heard, netflix has studios send them progressive video and lets them deal with de-interlacing. AFAIK, for enthusiasts, the best deinterlacer is "QTGMC" http://avisynth.nl/index.php/QTGMC http://avisynth.nl/index.php/QTGMC For stuff shot like post 2015, I don't think anyone is interlacing anymore. Everything is progressive. https://netflixtechblog.com/high-quality-video-encoding-at-scale-d159db052746 https://netflixtechblog.com/high-quality-video-encoding-at-s...
  - ubercow13 5y ago
    TV broadcasts are often still interlaced in some places
  - fomine3 5y ago
    I sometimes find newly released deinterlacing failed production video on YouTube. I wonder how is it failed, and why the production recorded the original video on interlace.
- toast0 5y ago
  Ideally, they deliver it to Netflix in the original form, properly marked as interlaced (or not) or for the small handful of shows filmed in 24p, as original films, marked as such (rather than presented with a 3:2 pulldown as originally broadcast). In practice (based on experience as a viewer), things are kind of messy, and sometimes the markings must be off, or someone did a really poor deinterlace, and there's visible combing all over, ugh. Netflix, or my streaming player, or my display can all deinterlace, so there's no need for the source to do it.
  - cogman10 5y ago
    From what I've read, Netflix has been investing quite a bit towards automatically detecting these sorts of issues and rejecting video that's been poorly handled by the studios. AFAIK, they reject interlaced content. From a compression standpoint, netflix wants everything to be progressive. Interlaced media (funnily) requires a lot more bandwidth to transmit with modern codecs. I say funnily because interlacing was a technique to save bandwidth for analog transmissions. It gives the illusion of a higher framerate. Unfortunately, modern video codecs work by tracking object movement from one frame to the next. Interlacing really messes that up requiring more bits spent for the same amount of quality. Some of the older codecs have interlacing built into the standard (mpeg2 and h264). Newer ones have banned it all together (VP9, AV1) due to the codec complexity it introduces for very little benefit. https://netflixtechblog.com/high-quality-video-encoding-at-scale-d159db052746 https://netflixtechblog.com/high-quality-video-encoding-at-s...
spookthesunset 5y ago
Technology Connections has a good video on how CRT’s work: https://youtu.be/l4UgZBs7ZGo https://youtu.be/l4UgZBs7ZGo
- Rendello 5y ago
  Captain Disillusion has a good video on interlacing specifically: https://www.youtube.com/watch?v=5eu_KjKsnpM https://www.youtube.com/watch?v=5eu_KjKsnpM
Hackbraten 5y ago
> Capacitors were still called condensers. Funny that in German, a capacitor is still a Kondensator to this day.
- trotFunky 5y ago
  The French word has kept the root too : "condensateur" !
- fomine3 5y ago
  Same in Japanese, コンデンサ.
jayd16 5y ago
Great pun in the title.

55 points by MindGods 5y ago

msla 5y ago

> We hit a strange truth about analog monochrome television: the vertical resolution is strictly limited: it’s the number of lines you draw. But the horizontal resolution, the resolution within each line, is basically infinite; it’s a purely analog signal. The only thing that holds it back is how quickly the electronics in your television can keep up. No, it's strictly limited by the bandwidth of the television signal. You could have infinitely responsive circuitry but you'd still have horizontal resolution limited by the bandwidth of the video portion of the broadcast TV signal. About all you can say is that analog TV does not have pixels. Anyway, here's a video (part of a series) on how analog TV works: https://www.youtube.com/watch?v=l4UgZBs7ZGo https://www.youtube.com/watch?v=l4UgZBs7ZGo Full playlist: https://www.youtube.com/playlist?list=PLv0jwu7G_DFUGEfwEl0uWduXGcRbT7Ran https://www.youtube.com/playlist?list=PLv0jwu7G_DFUGEfwEl0uW...

whatshisface 5y ago
>About all you can say is that analog TV does not have pixels. Color analog TVs have discrete patches of different phosphors.
- TazeTSchnitzel 5y ago
  Those aren't really pixels though: the signal can (and does) vary within them.

chrisseaton 5y ago

What does industry do about interlacing? I understand many TV shows were recorded and mastered on video with interlacing. When they re-release the TV shows for example for Netflix - what are they currently doing?

cogman10 5y ago
Last I heard, netflix has studios send them progressive video and lets them deal with de-interlacing. AFAIK, for enthusiasts, the best deinterlacer is "QTGMC" http://avisynth.nl/index.php/QTGMC http://avisynth.nl/index.php/QTGMC For stuff shot like post 2015, I don't think anyone is interlacing anymore. Everything is progressive. https://netflixtechblog.com/high-quality-video-encoding-at-scale-d159db052746 https://netflixtechblog.com/high-quality-video-encoding-at-s...
- ubercow13 5y ago
  TV broadcasts are often still interlaced in some places
- fomine3 5y ago
  I sometimes find newly released deinterlacing failed production video on YouTube. I wonder how is it failed, and why the production recorded the original video on interlace.
toast0 5y ago
Ideally, they deliver it to Netflix in the original form, properly marked as interlaced (or not) or for the small handful of shows filmed in 24p, as original films, marked as such (rather than presented with a 3:2 pulldown as originally broadcast). In practice (based on experience as a viewer), things are kind of messy, and sometimes the markings must be off, or someone did a really poor deinterlace, and there's visible combing all over, ugh. Netflix, or my streaming player, or my display can all deinterlace, so there's no need for the source to do it.
- cogman10 5y ago
  From what I've read, Netflix has been investing quite a bit towards automatically detecting these sorts of issues and rejecting video that's been poorly handled by the studios. AFAIK, they reject interlaced content. From a compression standpoint, netflix wants everything to be progressive. Interlaced media (funnily) requires a lot more bandwidth to transmit with modern codecs. I say funnily because interlacing was a technique to save bandwidth for analog transmissions. It gives the illusion of a higher framerate. Unfortunately, modern video codecs work by tracking object movement from one frame to the next. Interlacing really messes that up requiring more bits spent for the same amount of quality. Some of the older codecs have interlacing built into the standard (mpeg2 and h264). Newer ones have banned it all together (VP9, AV1) due to the codec complexity it introduces for very little benefit. https://netflixtechblog.com/high-quality-video-encoding-at-scale-d159db052746 https://netflixtechblog.com/high-quality-video-encoding-at-s...

spookthesunset 5y ago

Technology Connections has a good video on how CRT’s work: https://youtu.be/l4UgZBs7ZGo https://youtu.be/l4UgZBs7ZGo

Rendello 5y ago
Captain Disillusion has a good video on interlacing specifically: https://www.youtube.com/watch?v=5eu_KjKsnpM https://www.youtube.com/watch?v=5eu_KjKsnpM

Hackbraten 5y ago

> Capacitors were still called condensers. Funny that in German, a capacitor is still a Kondensator to this day.

trotFunky 5y ago
The French word has kept the root too : "condensateur" !
fomine3 5y ago
Same in Japanese, コンデンサ.

jayd16 5y ago

Great pun in the title.