Loosing file quality

[Sgt.Pepper]

I wasn't sure where to post this, so I hope this is an okay location.

I recently read that if you open up a jpeg file and then resave it, it loses quality. Is this true?
Is it only Jpegs, or all compressed images? Or even yet, all images i.e. Raw?
What other scenario must I be aware of where file quality can be lost? Any with music files, or video files?

 

[wrldwzrd89]

I wasn't sure where to post this, so I hope this is an okay location.

I recently read that if you open up a jpeg file and then resave it, it looses quality. Is this true?
Is it only Jpegs, or all compressed images? Or even yet, all images i.e. Raw?
What other scenario must I be aware of where file quality can be lost? Any with music files, or video files?

Yes, this is true of anything that uses lossy compression. JPEG files, MP3 files, and AAC files are 3 examples. These all suffer from so-called generational losses. This occurs because, in a typical editor, the binary data must first be decompressed to work with it. This step incurs no data loss. However, when the file is next saved, the only way to re-save it is to re-encode it. This process incurs all the losses from the original encoding, AND additional losses in the re-encode. This is where the quality deterioration occurs.

Not all compressed files have this problem. Anything that uses lossless compression, such as PNG images or Apple Lossless audio, does NOT suffer from generational loss each time it is saved.

 

[mongrol]

I wasn't sure where to post this, so I hope this is an okay location.

I recently read that if you open up a jpeg file and then resave it, it looses quality. Is this true?

No. But it can "lose" quality.

 

[Sgt.Pepper]

So I'd have to open the MP3, AAC file in someway where I'm resaving it for the file to degrade slightly? Not just say open it, play music, exit program?

 

[wrldwzrd89]

So I'd have to open the MP3, AAC file in someway where I'm resaving it for the file to degrade slightly? Not just say open it, play music, exit program?

Correct. Viewing a JPEG image or listening to MP3/AAC audio files doesn't degrade them. Editing these files DOES.