Is it possible to preserve quality?

[mst]

I have a video file (.MOV) and I want to add some effects to it. If I export afterwards using the exact same codec and settings used on the original file, will its quality remain exactly the same?

By the way, what is video quality measured in and where can I find it (so I can compare)?

[Baldrick]

No, you will lose quality. How much is hard to say depending the source and what kind of effects you add.

Video quality is measured by your eye.

[aedipuss]

no. you would need to start over with the original source material, not a rendered .mov.

your eyes.

[yoda313]

Also it depends on your output. If you need a regular standard definition dvd out of it and it was a high def mov file then there will certainly be loss no matter how much bitrate you use since you're changing the resolution.

If you keep it high def in either avchd or bluray form than you will lessen your loss by keeping the resolution the same as the input. However any editing will impact the file but how much depends on output bitrate used and your final destination format.

[deadrats]

I have a video file (.MOV) and I want to add some effects to it. If I export afterwards using the exact same codec and settings used on the original file, will its quality remain exactly the same?

By the way, what is video quality measured in and where can I find it (so I can compare)?

there is a principle in physics called thermodynamics, someone once said that the first 2 laws could be summarized as follows:

1) you can never get more out of a system than you put in.

2) you can't even break even.

this concept can be extended to practically any endeavorer, including video encoding.

with regards to you specific question, if you're adding effects, then it is not possible to end up with the "exact same quality" or else your attempt to add effects failed.

as for an objective metric for comparing quality, there is something called PSNR (peak signal to noise ratio):

http://en.wikipedia.org/wiki/Peak_signal-to-noise_ratio

there is also SSIM (structural similarity index):

http://en.wikipedia.org/wiki/Structural_similarity

and there are a few other methods that attempt to assign a numerical difference between 2 images as a way of measuring variations between sample A and sample B.

x264 has both -psnr and -ssim switches that can be used as an encoding parameter, do a few test encodes and see if in your case it provides some of what you hope to achieve.

[mst]

How about Exporting to image sequence (full quality, of course) then importing in the editing software? Would the resulting images _still_ lose quality?

[deadrats]

How about Exporting to image sequence (full quality, of course) then importing in the editing software? Would the resulting images _still_ lose quality?

by definition, if you're adding effects you are changing the image, you can't possibly end up with the same quality.

now if you're asking if you uncompress each frame into RAW format (or PNG's), import that into your editing software, apply the effects and then export the results, if you would retain most of the original quality, i would say yes, depending on the filters you use (like a good high quality denoise filter or color correction filter), you may even end up with a product that to the naked eye looks better than the original, but you are talking about a lot of work, the need for lots of hdd space, a powerful system, patience, skill on your part, as well as the right software.

the question is whether your project is worth all that effort.

[jagabo]

I have a video file (.MOV)... How about Exporting to image sequence (full quality, of course) then importing in the editing software? Would the resulting images _still_ lose quality?

If you recompress with any lossy compression codec you will lose quality. If you use high enough a bitrate (generally more than the original MOV file) it may not be very visible.

As far as quality is concerned, there is no difference between opening the MOV file directly in your editor or first decomposing the video into a series of uncompressed, or losslessly compressed images. The process of editing/filtering always* starts with first decompressing the video into uncompressed frames before the filters are applied. Actually, saving as images is likely to degrade quality more because most image formats use RGB 4:4:4 (at least as an intermediate) and your source video probably uses YUV 4:2:0. Simply the process of converting YUV to RGB and back to YUV is going to lose precision.

The process of decompressing the MOV file (to edit or to view) will give you frames with compression artifacts and fewer details than the original source. If you then recompress those frames with a lossy codec you will get another round of compression artifacts and detail loss.

* There are some programs that can perform some operations (like changing the brightness) on some videos without fully decompressing. Like EnoSoft's DV Processor.