This usually happens because kdenlive is not smart enough to deal with multiple types of files, especially different frequency. If you take a 44.1khz audio track and then add a 48khz track, you will definitely get the pops and clicks. Use a tool like audacity or similar to do two things, flatten the audio tracks to mono and at least make sure both tracks have the same frequency. I recommend changing both to 44.1khz. After Idid this and reimported the trac........

Use these flags: convert -alpha flatten -alpha remove "output.pdf" ljll.jpg And even the pesky black backgrounds should be gone after converting to jpg........