When exporting to mp4, can I specify an area of the timeline for higher quality compression?

[Adorable_Enigma16B8]

Hi

My current project exports fine apart from a part of the clip which has shapes with very sharp contrasty edges which just looks very jagged.  Small file size is crucial so I don't want to up the quality for the whole timeline.

I wondered if there was a way in Premiere Pro to mark out that small part of the timeline for higher quality treatment while leaving the rest of the sequence with current compression settings?

Thanks for any insight

Dan

[Bill Sprague]

There may be better ways to do it.  But, if it were me, I would set the work area bars around the part you want improved.  Then I would output that section with the highest quality you want and replace the old clip with the new clip in the project.  

[Peru Bob]

How ere those shapes created and imported?

Try different Variable Bit Rate settings in the export dialog.

[Warren Heaton]

Since the encoding methods available for MP4 have a GOP structure for the entire media duration, this isn't possible.  Even with an all i-frame format, it would be challenging.

Try the following:

• Hardware H264 encoding with a slightly higher Target Bitrate that what you're currentlly using.  For example, if currently using 10 Mbps, try 12 or 14.
• 2-pass H264 encoding with a Target  Bitrage set to give you the desired file size with a higher Maximum Bitrate.  For example, if currently using 10 Mbps and 12 Mbps, try 10 Mbps and 18 Mbps.

[ThioJoe · Accepted solution]

You could do it with ffmpeg but it will be a pretty manual process. I tested it out and it should work. Basically you'll be splicing together high and low quality encodings for different time frames.

For the setup you could approach it a couple ways, but for simplicity let's encode two versions with Premiere: One with the main target bitrate, and another with the higher bitrate. Meaning you'd encode the entire timeline for both versions into two separate files, then we'll extract specific time ranges from each, then combine them for a third final hybrid version.

First extract out the video parts you don't want to change like this, which you'd run on the normal quality version:

ffmpeg -y -i input.mp4 -ss 00:00:00 -to 00:00:01.500 -c copy output_part1.mp4

Where the -ss and -to parameters are starting and ending times, in "HH:MM:SS.milliseconds" format. To have it to go the end just leave out the "-to" part. So presumably you would do that command twice, one for part 1 (before the specially handeled part) and one for part 3, after it.

Then, you'd do the same thing as the command above, but doing it for the higher bitrate video and just for the segment that you want extra bitrate, which we can assume is part 2. 

Then you need to concatonate them together with a command like this:

ffmpeg -f concat -i list.txt -c copy output.mp4

Unfortunately I could not for the life of me figure out how to just put the list of files in the command line command, so you need to take the extra step of creating a list text file which will contain the list like this (don't forget the 'file' part at the beginning of each line)

file output_part1.mp4
file output_part2.mp4
file output_part3.mp4

Then that should work. I'll attach a test example (an animated emoji video about 3 seconds long), where the first half is around ~2000 kbps and the second half is extremely low (12kbps) to make the difference obvious.

Note: I would inspect the video because I've seen discussions about potentially having issues with keyframes considering the GOP encoding. It seems that might have been improved with recent versions of ffmpeg though not sure.

[MyerPj]

@ThioJoe , nice job on that post and testing! 🙂

[Adorable_Enigma16B8]

@ThioJoe Thanks for this great in-depth suggestion - exactly what I was after. Will give it a try

[MyerPj · Accepted solution]

Another tool you could use is: https://www.shutterencoder.com/en/

It offers features to Cut without re-encoding, merge some video together. Etc. Much like what @ThioJoe is getting at but this with a GUI and is a tool to keep around for many uses.

[Adorable_Enigma16B8]

@MyerPj Thank you - looks like a great tool.

[MyerPj]

You might also experiement with exporting in a high quality (DI) format like prores LT or such, then make an h.264 from that, just to see the results. You can place the ProRes into Shutter Encoder and make the h.264 (or 5) there.