Ever since I got my DV500 video capture/editing card I’ve done a lot of experimenting with capturing and transcoding video. Over the years I’ve come to learn that reprocessing, transcoding and resizing video is actually a very finicky process if you dont want to mess up aspect ratios and have interlacing artefacts. This stems from the fact that SDTV video is being derived from analogue sources (PAL or NTSC), where frequencies and timings define things, not nice square pixels as in the digital world. Add to this the fact that different capture hardware chipsets and drivers have their own ideosynchrosies when it comes to exactly what part of the image is captured!
Examples of the hidden complexities:
- 720×576 4:3 PAL video is not 4:3 over the 720 pixels. Its close at the common 704×576 resolution but even then not exact.
- some interlaced video formats have the odd lines first, others have the even lines first, sometimes the first line is always black…
- pixels in standard definition digital video are rarely square
- a 720×576 PAL image is NOT the same image area as a 720×480 NTSC image. The relationship is much more complex.
In my case, the DV500 captures to 720×576 DV and I’m converting to DVD standard 704×576 MPEG2. Whilst software exists that automates the process, I’ve found that to have more control over the process (particularly so filters can be applied) you need to understand more of the details of video.
My efforts currently involve the use of Adobe Premiere 6 for capture and editing, VirtualDub for deshaking and TMPGEnc 2.5 for further filtering and encoding. You might wonder why I’m not going to DivX or XVid. My reasons include:
- I want something playable by any DVD player
- I dont want to de-interlace, I want to keep the video close to its original form
- I’m not out to save bits but rather preserve the video digitally
I’ve found playing MPEG2 video using the DScaler decoder and ZoomPlayer gives silky 50fps frame doubled video which exceeds the results from de-interlacing to 25fps. So I’m sticking with that and in subsequent articles I’ll write up how I process the video.
I’ve placed a list of useful pages on video formats here.