Blistering fast with RAW files until.. I peruse Adobe DNG files

Been using FRV for about 6 months now to cull after shoots and prior to LR edit.
Works beautifully most of the time -- BUT - if I let LR convert a shoot to DNG and then try to review in FRV, all speed is lost and FRV is nearly unusable.
I've tried the various settings, DNG creation paths (with / without jpegs), various FRV settings etc. but DNG format just seems to gum up the FRV works.
My solution has been to not convert to DNG. But I am curious what is going on. Am I missing something?

Dear Sir: Could you please upload a DNG sample and e-mail us a link, ?

thanks and sent file to you!

Dear Sir: Thank you for the sample. The conversion process you applied to produce this file make a linear DNG, that is the file is demosaicked. That means 4x more data after unpacking. Of course the processing is times slower. On top of that, the file contains lossy 8-bit data, here is the relevant portion of metadata [EXIF] 0x0102 BitsPerSample: 8 8 8 [EXIF] 0x0103 Compression: Lossy JPEG [EXIF] 0x0106 PhotometricInterpretation: Linear Raw [EXIF] 0x0115 SamplesPerPixel: 3 If you are forced to use such a format, please try setting Preferences -> "GPU Processing" -> "Process RAW data on GPU" to "All raw files" - that will speed things up a lot if your video card / GPU is one of the modern models.

Stay away from DNG. I made that mistake 5 years ago, and had problems with adobe lightroom created DNG in so many different programs. It's supposed to be a good open format, but most people learnt to stay well clear of it by now.

Dear Sir:

The culprit here may be not Adobe themselves, but other parties.

Adobe software records and reads DNG files according to the published documentation, third-party software may implement the specifications only partially, hence there are incompatibilities.

You can find the same problems with JPEGs and TIFFs as soon as they are recorded according to specifications but in a less popular format. I remember many cases when CMYK JPEGs were displayed erroneously, from black screen to acid colours, depending on the software. Also, a lot of applications dealing with TIFF / JPEG fail to comply with colour management routines, displaying wrong colours as a result.

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