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Forums Compression Techniques DG Specs — too compressed?

  • DG Specs — too compressed?

  • Naveen Mallikarjuna

    June 27, 2007 at 8:21 pm

    I’m trying to encode a spot from AVI to MPG for DG Fastchannel (we’re trying to get set up with them).

    I’m using MainConcept and Sorenson.

    I followed DG’s setting to a T (they even sent me screenshots for Main Concept), and the results I’m getting are less than stellar.

    The spots look noticeably compressed down from their original version.

    On top of that, Main Concept only allows a maximum bitrate of 15 MBs for video — why not higher?

    Does anyone have any experience with Main Concept? What am I doing wrong? Or is that just how DG spots look?

    Naveen

  • Craig Seeman

    June 28, 2007 at 4:11 pm

    I use Episode Pro and use 25Mbps 2 pass CBR to ensure my entire encode is at their peak acceptable data rate.

    So far I’ve found the best way to confirm the quality of the encode is with VLC.

    I’ve found that MPEGStreamclip and Quicktime don’t seem to playback the program streams well.

    You don’t mention your source AVI but I’ve even got good results with DVCAM MOV source (I’m on Mac so I’m using MOV).

    AVI is a wrapper so what’s in there can make a big difference.

  • Naveen Mallikarjuna

    June 28, 2007 at 4:37 pm

    I’m on a PC with a Matrox LE card. I tried to output to both a Matrox AVI and the generic Windows AVI w/o compression. Got the same results.

    I wonder if I should try a different file type (such as MOV)?

    What I don’t get is why MainConcept or Sorenson would produce such compressed-looking results at 25 MBps. I imagine there are plenty of people on PCs making spots for DG. I can’t believe they would be sending out spots that looked like what I’m seeing.

  • Craig Seeman

    June 28, 2007 at 5:04 pm

    [Naveen Mallikarjuna] ” tried to output to both a Matrox AVI and the generic Windows AVI w/o compression. Got the same results.”

    But what’s your source codec. AVI is the wrapper. What’s the codec?

    Try a 25Mbps 2 Pass CBR encode.

    Also you didn’t say how you’re testing your encoded file. What Player? It’s decoder can have big impact on what you see.

  • Naveen Mallikarjuna

    June 28, 2007 at 5:28 pm

    The codec on the first try would be the Matrox Axio codec. On the second try it was whatever the codec is for a generic Windows AVI. Unless I’m getting something wrong.

    As for the player/decoder, all I did was import the encoded mpg file into my NLE and view it on an external monitor.

    Is there a good decoder for the PC that can play an MPEG-2 stream well?

  • Craig Seeman

    June 28, 2007 at 6:42 pm

    VLC plays MPEG2 Program streams well for me.

    Codec as in DV, 8 or 10 bit Uncompressed, DVCPro50, etc.

    Try avoiding any proprietary codec and see what happens.

  • Naveen Mallikarjuna

    June 28, 2007 at 8:06 pm

    Well, the Matrox codec is a proprietary codec made by Matrox Systems. The Windows codec is 8-bit Uncompressed.

    I’ll output to DV and DVCPro50 and give it another try.

    I downloaded VLC and gave it a quick test — the mpg files certainly looked better through VLC than with my NLE or Window Media Player.

    Do you know if VLC can output to an external monitor? If I can see it on an actual TV then I’ll feel confident about it.

  • Erik Pontius

    June 29, 2007 at 3:12 am

    If you imported it into your NLE, it most likely converted the high bitrate MPEG file into another codec in order to use it in the timeline and export it to a monitor. Probably not a true representation of your MPEG file.

    Erik

  • Craig Seeman

    June 29, 2007 at 12:41 pm

    There’s a Video/Video Device menu choice but I don’t think it’ll pass to a TV Monitor.

    If you’re within broadcast specs (video scopes, audio meters on your system) and it looks good in VLC, you can probably send it off to DG.

    DG has certification process requiring 5 tests so they’ll tell you if there’s an issue with your workflow/encoded files.

  • Craig Seeman

    June 29, 2007 at 12:45 pm

    It really depends on how the NLE handles the respective codec.
    One should really test on a player that can handle MPEG2 Program Stream natively. You’d think that MPEGStreamclip would do this but it doesn’t handle Program Streams well.

    VLC does. What I see in VLC is what I see when my spots are distributed by DG to local cable stations (understanding that VLC/Computer display is not color/gamma accurate to TV).

    [epontius] “If you imported it into your NLE, it most likely converted the high bitrate MPEG file into another codec in order to use it in the timeline and export it to a monitor. Probably not a true representation of your MPEG file.

    Erik

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