Finishing Using Compressed Versus Uncompressed Media

When you are deciding how to ingest your media, a common question is how best to handle compressed formats if you know you want to finish at the highest possible quality later. One of the advantages of working with compressed formats such as DV-25, HDV, AVCHD, DVCPRO HD, or XDCAM is that you can ingest them natively, at their original resolution and quality, with relatively modest storage and processor requirements (at least with the current generation of Mac computers). However, when the time comes to finish your program, adding the final titles, design, and effects and doing color correction prior to mastering your program, questions sometimes arise about whether working with such highly compressed media is appropriate.

This section addresses why preemptive upconversion (transcoding a compressed media file to an uncompressed media file) before you start the finishing process may be unnecessary and when it might provide advantages. It also notes when, at the end of the finishing process, upconversion is a necessary step.

Does upconverting compressed media from one codec to another improve quality?

From a strictly qualitative standpoint, there is virtually no difference between a highly compressed media file and the same file transcoded—at the same frame size and frame rate as the original media—to a higher-quality codec (such as one of the Apple ProRes or Uncompressed codecs) using one of the Final Cut Studio applications. For the same reason, there’s no qualitative advantage to simply transcoding to another codec during ingest.

Another possible approach is to upconvert previously recorded compressed media by connecting the SDI or HD-SDI output from a video deck or camcorder to the input of a video capture card, thus using the deck’s circuitry to upconvert the compressed signal to an uncompressed media file during capture. However, this doesn’t actually provide access to any additional pixels or samples of information. Depending on the hardware you’re using, there will be some filtering and interpolation of the video signal’s components, but this process simply alters the data that was originally recorded. It’s debatable how much of a visible increase in apparent image quality is provided, and whether it’s worth the additional hassle.

The bottom line is that simply transcoding media from one codec to another in software does nothing to improve image quality. Doing a hardware upconversion might or might not have a noticeable effect on certain kinds of compression artifacts, but in most instances it’s probably easiest to keep your media in the format in which it was originally shot during the offline edit, preserving the data exactly as it was captured.

Keep in mind that once data has been discarded by compression in the camera at the moment it’s shot, it is not retrievable, no matter what format you upconvert it to.

Note: Upconversion is not the same as format conversion, in which you change a clip’s frame size, frame rate, and field handling in addition to the codec it uses. When doing format conversion, using specialized software (such as Compressor), third-party plug-ins, or dedicated hardware can result in a dramatic improvement in the final result. For more information about format conversion, see Format Conversion When Finishing Mixed-Format Sequences.

Are there other advantages to upconverting compressed media?

There are other legitimate reasons to transcode media from one codec to another. For example, you may find that working with some highly compressed formats natively is more processor-intensive than working with versions of the same media transcoded to one of the Apple ProRes codecs.

Another good reason to transcode is if the native resolution of the media is slightly different from the frame size at which you want to finish the program, and you don’t want to deal with resizing issues. For example, many compressed high definition acquisition formats are anamorphic; DVCPRO HD may be recorded at 960 x 720, and HDV may be recorded at 1440 x 1080. If you prefer working at the nearest full-raster frame size in preparation for finishing, you may choose to upconvert your media to 1280 x 720 or 1920 x 1080.

Of course, that’s not the whole story.

Why is it important to upconvert compressed media at the end of the finishing stage?

When the time comes to color correct your program, near the end of the finishing stage, you’ll be reprocessing and rendering every clip to which you either make adjustments or apply effects. Whether you’re working in Final Cut Pro or in Color, all image processing is done in an internally uncompressed data space, regardless of the source format. Because you’re adding filters and vignettes and performing other high-quality image-processing operations that will ultimately benefit from less compression, this is the appropriate time to render your compressed source media using an uncompressed or lightly compressed format suitable for mastering. This lets you retain the high quality of the image-processing operations being performed and prevents you from double-compressing your media unnecessarily. There are two ways of transcoding compressed media during rendering.

  • If you’re grading your program in Color: Make sure that your program’s media is reconformed to its maximum native quality (or better) prior to sending it to Color, even if the native format is compressed. You can send either compressed or uncompressed media to Color, as long as the media is in a format that’s compatible with Color. In Color, you specify the codec used to render the final color-corrected media using the QuickTime Export Codecs pop-up menu (in the Project Settings tab of the Setup room), and this is the point at which the internally uncompressed image data that’s processed by Color is written to a superior media format suitable for mastering. See the Color documentation for more information.
  • If you’re finishing your program entirely within Final Cut Pro: The best solution for high-quality mastering is to change your sequence’s codec using the Compressor pop-up menu in the General tab of the Sequence Settings window. It’s also a good idea to open the Video Processing tab and make sure the bit depth is set to an appropriate quality for your program and that the Motion Filtering Quality pop-up menu is set to Best.

If you follow either of these workflows, it’s not necessary to preemptively transcode your media in preparation for finishing, because it’s simpler and easier to transcode your media during rendering, and you get the same results. For more information about rendering your final media using a mastering codec, see the Final Cut Pro and Color documentation.