Mediaconvert H264 keeps failing

I would recommend opening a support case to help troubleshoot your issue.

If you can't transcode files that were successfully transcoded by EMC day before, please open support ticket in aws and inform about possible regression.

It sounds like you're experiencing an issue with MediaConvert related to variable frame rate (VFR) input. This is a known issue that can occur even if you haven't made recent changes to your workflow.

The error message suggests that your input video has a variable frame rate, which is causing conflicts with the "Maintain frame count" setting in your output's Frame rate conversion algorithm. This can happen if the source file's characteristics have changed or if there's been an update to how MediaConvert handles VFR inputs.

To resolve this issue, you can try the following:

1. Change the Frame rate conversion algorithm in your output settings. Instead of "Maintain frame count," try using "Duplicate drop" or another option.

2. If possible, check your input file to confirm if it indeed has a variable frame rate. You can use tools like FFprobe to analyze the file's properties.

3. If the input does have VFR, consider converting it to a constant frame rate (CFR) before submitting it to MediaConvert. You can use FFmpeg with a command like: ffmpeg -i input.mp4 -vsync cfr -c:v libx264 -c:a copy output.mp4

4. If you need to process the file as-is, you might need to adjust other settings in your MediaConvert job, such as explicitly setting the output frame rate or using the "Force CFR" option if available.

5. If the problem persists across multiple input files, it may be worth reaching out to AWS support for further assistance, as there could be a broader issue with the service.

Remember that MediaConvert can be sensitive to input file characteristics, and sometimes updates to the service can affect how it handles certain types of inputs. If you continue to face issues, consider submitting a support case to AWS for a more in-depth investigation of your specific workflow and files.
Sources
MediaConvert introduces audio-video sync issue | AWS re:Post
Bug in MediaConvert Output setup blocks resolutions that are actually supported by AVC, and still encodes anyway if you trick it | AWS re:Post