blackmagic decklink SDI, fiable ?

Bonjour,

je viens solliciter vos remarques sur la blackmagic decklink SDI, produit tellement intéressant qu'il en est douteux...

en effet, le site du constructeur l'annonce autour de 300$ ce qui est une misère comparé aux prix de carte du même type en externe...
spécification technique : (cf colonne de gauche) Blackmagic Design: DeckLink Tech Specs

je comptais simplement m'en servir de carte d'acquisition pour mon scope DNW-A65P (BetaSX)
en fait, ce qui me chagrine, c'est qu'une carte d'acquisition SDI externe coûte environ 600euros de plus... que penser ?

j'ai bien trouvé la fiche d'avis de la carte, mais aucun retour des utilisateur,
est-ce du matériel fiable ou vais-je dépenser 300euros dans le vent ???
si vous avez déjà acheter du blackmagic ou si vous avez des infos, je suis preneur !

merci d'avance

 

voilà ce que je trouve...

"Customer Buzz
"Excellent capture card, not suitable for print or broadcast though" 2010-04-11
By Darren R. Starr (Oslo, Norway)
This card is a fantastic buy at the price point which they provide it. For a fraction of what competitor cards cost, this card is an ideal ingest device able to capture SDI and HD-SDI signals at full rate on just about any modern PC. I've been a user of Blackmagic for the past 4 years and have been every pleased with their products. If you're a using this card to capture from a Digibeta deck or a HDCAM (not SR, that requires dual-link) for the purpose of producing file based formats or for DVD and Bluray production, this card is nothing short of great.

It's able to capture video and audio from a source with little effort.

There are a few gripes I have with the card.

1) Reference clock.
It doesn't always do a great job without having access to house clock. This is silly on a PC capture device since a PC can derive the source clock from the SDI signal. Reference clock should only be necessary for play-out, to synchronize with other sources. For a single point to point connection reference clock should not be needed.

2) Drop frames requires full recapture.
SDI and HD-SDI are amazing in the fact that audio is synchronized to a specific line of video. Since Blackmagic's devices demultiplex audio and video while capturing, sync isn't guaranteed to be perfect. The only way to ensure a perfect capture is to capture from start to end. If Blackmagic wanted to do this job better, when they detect frame drops, they would rewind the source media and recapture from the drop. Alternatively, it would work to capture the individual dropped frames with audio afterwards. The way they have done it means that if you dropped a frame an hour into a capture, the entire hour has been wasted. Time to start over again.

3) Play-out does not follow SDI spec and is spectacularly bad for broadcast.
As an engineer that designed hardware CODECs for SDI, HD-SDI and 3G-SDI sources, I spend hours a day decoding streams sample for sample and producing valid streams to play out as well. SDI and HD-SDI are extremely hard to get right and Blackmagic simply doesn't. The Blackmagic card ALWAYS outputs 16 channels of audio, whether it is present or not. This is wasteful and confusing. Additionally, the Blackmagic card does not implementing the switching line of the signal. This means that audio is transmitted on the switching line which by definition should be clear. This will trigger alarms up and down the production pipeline if any resyncing needs to occur. I generally work in a PAL environment, but this is catastrophic in a NTSC environment. Blackmagic also does not implement ECC for HD-SDI audio. This is probably a good thing since during testing, I've learned there are way too many interpretations of the spec and the only safe thing to do is to just leave it out. Blackmagic however should at least implement Sony's implementation of ECC on HD-SDI audio since ECC is extremely important on tape based media. Bit rot over time can be somewhat avoided using ECC. The correct solution would be to implement Sony's interpretation of the spec and make it an option in the driver whether to enable it or not.

So overall, while this card is clearly unsuitable in a professional broadcast environment and probably should never be used for printing to tape, it is an amazingly good solution for ingest of SDI and HD-SDI signals."

 

conclusion

si j'en crois la dernière ligne, cette carte n'est même pas fichue de faire un export sur bande...
ça expliquerai son prix
visiblement elle est uniquement dédiée à la capture