The Case of the PAL Reversed Fields
James Paterson
Australian Television Archive, Broadcast Film & Video Digitisation Services
Over the last year or so we have been trialing the use of AJA Kona's LHI analogue digitisation solution. Whilst its a mostly robust and stable product, its major downside has been the strength of its drivers.
Earlier drivers were disappointing with numerous bugs, among them - no support for PAL capture or codecs in Adobe Premiere. CUDA acceleration has to be turned off if you want stability or interlaced output for playback to an external monitor - and an ongoing bug of certain file formats defaulting the card to either 525i, or 720p output.
Recently a long awaited update of drivers was released which brought full PAL capture capabilities back to premiere, but with a new issue: All captures to the domestic DV25 format suddenly began playing back with the fields reversed.
Upon investigation it became evident there was a major difference in the file/codec ids: the old drivers were capturing with the codec id: dvcp "Apple DV - PAL" (ie domestic DV - lower field first). The new drivers were capturing as codec id: dvpp "Apple DVCPRO - PAL" (broadcast DV upper field first)
It seemed that with the new drivers, Kona had removed domestic dv compliant capture functionality and replaced it with a broadcast DVCPRO (upper field) variant, but the question is WHY? as part of its options if you needed broadcast compliant upper field first capture, Kona already offered DVCpro50 (upper field first) as a broadcast DV option.
Why then remove the domestic variant ?
In many situations domestic clients or projects still require the domestic DV25 format (lower field first). It does not make for happy clients now finding their captures now display flickery! Whilst there is a work around by manually reversing the fields and then re-rendering, its an inconvenient and time consuming problem.
But the question remains, why did Kona change it? Previously you at least had the choice.
Perhaps the easiest way to solve this problem is by giving you the option to choose field order at the capture stage, it would solve a lot of headaches, and i suspect a lot of eyes from watching flickering movement!
What are your thoughts? Have you used the Kona LHI products yourself, are my observations correct/incorrect or have i misinterpreted something? - drop me a line. I'm always willing to talk and learn more
