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Composite Video and quality issues



  • After having the opportunity to work more and more with pro video interfaces ( I am running my projectors with HDMI extended over SDI, cameras in over SDI) I had to go back to composite. I run the composite form a blackmagic ATEM switcher. I am using only belden 1505f cable for all connections and 75ohm BNC (with the 1505f) from cameras.

    I noticed the lack of detail in the SD composite output. I think I have made the most ideal situation for a composite signal path but it still looked far less than perfect.
    I looked to the internet for answers and found a info/test DVD from SMPTE. Here I learnt a lot. SD actually looks amazing, but composite video has to discard a huge amount of the information in the signal. I have a camera (sony EX-1), that has composite, SDI and component outputs. I began to do a more serious comparison with the output signals. The results were not really surprising but I was still a little shocked.
    Composite video, although it can look good discards so much of the video information it looks crippled. It under these circumstances it does look very good with high quality connections gear and cameras, but compared with the others (HDMI, component and SDI), there was so much detail and colour lost it was disturbing. There is currently a big drive to go HD, I also did it and HD is obviously better, but a well designed SD system (without composite or S-video connections) can look amazing- really.
    If anyone is so inclined do a simple test, download a smpte test pattern, not just the colour or luminance one, but the one with small fine lines, if you can connect HDMI component or SDI (using a smpte standard like SD PAL) check the detail and colour, then swap to composite and see how much information you actually get.
    As I said I was not surprised the pro formats were better, but I was surprised how much information was lost.
    Why make this post?
    There is always talk of better quality images in Isadora, However before we all start hassling Mark to make our stuff look better, we should really examine the limitations of our gear- I also did a comparison with DV encoders such as the canopus vs. the blackmagic capture gear, the canopus can only ingest composite (unless you have the very expensive ADVC1000), the DV signal takes a lot of work to turn into frames and it also starts as composite. An SDI or HDMI input at the same resolution gives much better results with lower CPU overhead.
    I am having a rethink of several of my setups, after these tests I am very impressed with Isadora's quality but the old rule still holds true; garbage in garbage out.
    Fred

  • Tech Staff

    Fred this is a brilliant post!

    I can't add to it or comment any further really. But I smiled when I read "garbage in garbage out!" love it!

  • Tech Staff

    @Fred

    Thank you for the post. Since a few months we are solely using SDI wenn possible. The Blackmagic HDMI --> SDI and SDI --> HDMI convertes are cheap simple and you get great quality. I even prefer it over the optical fibre we have, not in terms of quality but in terms of simpleness and robustness.

    Best,
    Michel



  • Dear Fred,

    As always, you provide a high degree of enlightenment to this community. Thank you for the effort you put into this post.
    Best Wishes,
    Mark
    (P.S. I really am around to be hassled though; it's just a matter of what can get done first. ;-)

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