Capturing OTA - ATSC SD programming

Discussion in 'Computers' started by Gary_E, Mar 21, 2005.

  1. Gary_E

    Gary_E Second Unit

    Joined:
    May 6, 1999
    Messages:
    366
    Likes Received:
    0
    Trophy Points:
    0
    I’ve read many posts, both on HTF and AVS, concerning capturing digital and high-def programming. High-def captures do not interest me at this time because I do not have a PC connected to my HT, so viewing high-def captures is not possible. This kept my interest focused on capturing the higher quality SD ATSC signals offered by my local OTA networks.

    My experiment began using my Samsung SIR T-150 high-def receiver. I connected the T-150 to my All-In-Wonder 7500 video card with S-video and composite cables and I was able to capture the ATSC signal, producing a high quality capture. The drawback to this process was that the T-150 was in a different room, so running the cables and changing channels was a pain.

    When a local store offered the LG 4200 high-def receiver for under $150, I purchased a unit to be used exclusively for ATSC captures. There would be no connection to a high-def monitor, only an S-video and composite audio connection to the dongle on the ATI card. I left the output switch on the 4200 set to 480i, although I believe this setting is irrelevant since the S-video and composite outputs are 480i regardless of the output setting on the STB.

    Finding the correct combination of settings between the capture card and the STB was the trickiest part of the process. After experimenting with different capture settings on the ATI card and different display ratio settings on the STB, the resulting captures were very good, far superior to the analog captures of the same program.

    ATI 7500 capture settings used with Multi Media Center version 9.1.
    Format - MPEG-2
    Standard - NTSC (525)
    Resolution - 720x480
    Audio Format – 48,000 KHz, 16Bit, Stereo

    For 4:3 programming, the STB’s ratio setting is set to ‘CROPPED’, capturing the full frame image without the window-box black or grey bars on either side.
    For 16x9 programming, the STB’s picture ratio is set to ‘SET BY PROGRAM’. This setting is deceiving because while viewing the screen during the capture, the image is displayed both letterboxed and window-boxed. However, when playing back the captured file, the image is displayed letterboxed only.

    This process is not without problems. When capturing from the STB, the entire program stream is recorded. This includes a thin, moving, dotted line, running either above, below or on the side of the letterbox or window-box outer borders. I assume that if this file is played back on a regular TV, this line (data stream) would be beyond the over scan parameters and not be visible. My solution is to re-encode the video, slightly cropping the image, to eliminate the line.

    -Gary
     
  2. Ken Chan

    Ken Chan Producer

    Joined:
    Apr 11, 1999
    Messages:
    3,301
    Likes Received:
    0
    Trophy Points:
    0
    SD is already encoded in MPEG-2 (like HD, but at a smaller resolution and bitrate). Have you tried capturing the transport stream directly? That way, you don't have the digital-to-analog-to-digital conversion you get capturing through S-video or composite.

    You would need a STB with a FireWire connection, or an ATSC tuner card for the PC that has capture functionality, which will simply dump the transport stream on-disk. You then need a program that can read the transport stream, and strip off the transport bits to convert it to a regular program stream.

    Of course, given the current state of things, that wouldn't necessarily be easier, and the incremental quality improvement from what you're doing now may not be as big as going from pure analog in the first place, but it's something to consider.
     
  3. Scott L

    Scott L Producer

    Joined:
    Feb 29, 2000
    Messages:
    4,457
    Likes Received:
    1
    Trophy Points:
    0
    Echoing Ken, it would be best to just capture the TS. Then you won't have to worry about encoding settings or quality loss.

    If your receiver doesn't have a Firewire output grab a MyHD-120/130 or Fusion HD card.
     
  4. Gary_E

    Gary_E Second Unit

    Joined:
    May 6, 1999
    Messages:
    366
    Likes Received:
    0
    Trophy Points:
    0
    I should have prefaced my post with the fact that I spent the last few months tweaking my system and have it running the best it has ever run. I was reluctant to make changes inside the PC by adding new video cards etc.

    Capturing from a separate STB made sense to me because it required no changes to my existing configuration and because I was able to get the STB at a great price.

    I am very pleased with the results. The post-capture editing is fun and is the part of the process I enjoy most. Maybe my next step will be an HD capture card but for now I like this rig.

    Thank you for the replies and suggestions.

    -Gary
     

Share This Page