Am I going nuts? Inexplicable file size reduction!

[Alexander Wolf]

So to answer my own question: I discovered that it is the data rate that causes the difference in file size. Data rate is not shown when you type Cmd+i on a file that’s not opened in QT. When you open it in Quicktime and then click Cmd+i, it shows the data rate, I accidentally found out.

I have no idea why the data rate changed but I’m sure it’s a user error ;-(

Now all I have to do is figure out how to get the data rate back to where it was…

[Alexander Wolf]

Since there is no Apple Compressor forum (?) and the Compression Techniques forum seems like a very lonely place, I’d like to call out to some sharp souls out here and help me figure out how to change data rates in Apple Compressor, specifically in Photo-Jpeg.

[Tero Ahlfors]

The Photo-JPEG codec only has a quality slider. The data rate is set by the codec.

[Alexander Wolf]

But how come exporting photo-jpeg from my iMac 5K generates a 15MB file from a 6 second HD clip while the exact same clip generates a 200MB file on my MB Pro?

Has Apple reduced the base setting for data rate in the photo-jpeg setting by factor 14 in their Compressor upgrade from 4.2 to 4.2.1? (no mention in their release note) Weird!

I hope it’s not too much to ask but could someone please export a 6 second HD clip from Compressor 4.2.1 in photo-jpeg and see how big the file turns out?

Would really appreciate it.

[Tero Ahlfors]

A six second clip of HD bars and tone is about 15 megs from AME with the QT Photo JPEG codec and AAC audio. Same clip is about 8 megs from Compressor 4.2.1 with the same settings. Data rate from AME is about 20 Mbit/s and Compressor about 10 Mbit/s.

Either this is some one off mystery bug or an user error.

[Robin S. kurz]

[Alexander Wolf] “But how come exporting photo-jpeg from my iMac 5K generates a 15MB file from a 6 second HD clip while the exact same clip generates a 200MB file on my MB Pro?”

Question is, which preset are you using?? Because there are no default P-JPEG presets in Compressor, so you must have made it yourself in both cases. But the 15MB file-size would be the one to expect, yes. The only explanation imho could be, that you in fact are not using the exact same preset and the the latter simply isn’t even set to P-JPEG. Clips of all types here show a size roughly between 15 and 25MB. If this were H.264 I’d suspect you’re using different entropy modes.

No offense, but I’d have to go with PEBKAC.

Otherwise simply post the preset file somewhere for others to look at or rather try out themselves.

– RK

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[Alexander Wolf]

Thanks, Tero.

Isn’t that an extremely low data rate? 10mbit/s?

I’ve been generating files at much higher data rates for the last year on my iMac and for some reason this has changed in the last month. The only thing I can think of is the Compressor upgrade. Why would I change the Compressor settings when it has worked for me for the last year?? (I never even use Compressor, except when I created a preset for FCP X a long time ago)

[Alexander Wolf]

I’ve been using a preset I created: New Setting-QT movie – in the inspector pane I changed the QT settings to photo-jpeg. That’s all. I just created new settings in the exact same way on my MB Pro and iMac: 200 MB file vs an 18 MB file.

I’ve also checked on Pond5 to see what another contributor’s file sizes are for photo-jpeg. They are much, much higher than 15MB for a 6 second file. They approximate what I’ve been producing in the last year- until something inexplicably changed…

[Alexander Wolf]

No takers? I posted some screenhots but I guess this will remain a mystery…

[Alexander Wolf]

I thought Robin S. Kurz would have an opinion on my screenshots! Maybe you didn’t notice but I shared the settings from Compressor 4.2 and 4.2.1.
I also included the 2 QT files showing their respective specifications. Can you figure it out, Robin?