Yellowish lines in video after editing it

Hi,

This seems like rendering or compression artifact issue. Since the lines aren't visible during editing but appear after export (even without significant color grading), and persist across different videos using the same export settings, let's break down the potential causes and solutions.

The fact that it happens post-export points towards the rendering/encoding process within CapCut or how the chosen settings interact with your specific footage or system.

Here’s a systematic approach to troubleshoot this:

1. Confirm the Issue is Pre-Upload:

   • Before uploading to YouTube or any platform, play the exported .mov file directly on your computer using a reliable media player (like VLC Media Player, which is good at handling various formats).
   • Do the yellowish lines appear in the local file?
     • If YES: The problem lies within CapCut's export process or settings. Focus on steps 2-6.
     • If NO (Only appear after YouTube upload): The issue is likely YouTube's re-compression amplifying very subtle artifacts present in your export, or YouTube introducing them. Focus on step 7, but also consider steps 2 & 3 as optimizing the export might help YouTube process it better.

2. Experiment with Export Settings (Most Likely Culprit):

   • Using high compression rates can introduce artifacts such as blocking, blurring, or color anomalies. Adjusting your compression settings might help mitigate these issues. Consider the following adjustments:​
   • Container Format: Try exporting as MP4 instead of MOV. While MOV is common (especially on Apple systems), MP4 is more universally standard for web distribution and sometimes handles compression differently.
   • Codec:
     • Try exporting using HEVC (H.265) instead of H.264. HEVC is more efficient, especially for 4K, and might handle color information differently, potentially avoiding the artifact.
     • If sticking with H.264, check if CapCut offers different H.264 profiles (e.g., Main, High). Experiment if options exist.
   • Bitrate: You mentioned "High." See if CapCut offers a "Recommended" setting or allows you to set a specific numerical bitrate. Try the "Recommended" setting first. If that doesn't work, try manually setting a higher numerical value (e.g., 50,000 kbps or 50 Mbps for 4K SDR) as a test, even if the file size is large. This checks if the "High" setting isn't quite high enough and is causing compression artifacts (banding) that appear yellowish.
   • Adjusting the bitrate can influence both the file size and quality. A higher bitrate generally improves quality but also increases file size. Finding a balance is key. Some users have reported that switching from a 2-pass Variable Bitrate (VBR) to a 1-pass Constant Bitrate (CBR) can reduce artifacts. Using a 1-pass CBR with an average bitrate of 6.8 Mbps may eliminate noticeable artifacts without significantly increasing file size.
   • Resolution: As a test, export a small segment at 1080p instead of 4K using your usual settings (or MP4/H.264). Do the lines still appear? This helps isolate if the issue is specific to the high resolution.

3. Check CapCut's Rendering/Hardware Acceleration Settings:

   • Look in CapCut's preferences or settings (under Performance, Export, or Advanced settings).
   • Find options related to Hardware Acceleration, GPU Acceleration, or Encoding Engine.
   • Try disabling hardware acceleration for encoding/export and use software encoding only. Sometimes GPU drivers or specific hardware interactions can cause rendering glitches. The export will be slower, but it's a key test. If this fixes it, you may need to update your graphics card drivers or keep hardware acceleration off for encoding.

4. Color Space Issues:

   • Check if your source footage is HDR (High Dynamic Range) while your CapCut project or export settings are SDR (Standard Dynamic Range), or vice-versa. Mismatches during conversion can sometimes cause color banding or shifts.
   • Look for any Color Space settings in your CapCut Project Settings or Export Settings (e.g., Rec.709 for SDR, Rec.2020/HLG/PQ for HDR). Try to ensure consistency or perform a proper conversion if needed (though CapCut's controls for this might be limited).

5. Clear CapCut Cache:

   • Sometimes corrupted cache files can cause unexpected behavior during rendering. Look for an option within CapCut's settings to clear the cache or temporary files.

6. Update CapCut & Graphics Drivers:

   • Ensure you are using the latest version of CapCut. Bugs get fixed in updates.
   • Ensure your computer's graphics card drivers (NVIDIA, AMD, Intel) are up-to-date.

7. If Lines ONLY Appear After YouTube Upload:

   • This suggests YouTube's compression is the main culprit, likely struggling with gradients or subtle color variations in your video.
   • Optimize for YouTube: Exporting using MP4, H.264 (or HEVC if supported well by YT), and a sufficiently high bitrate (as per YouTube's recommendations for 4K) is generally best. Even if the lines aren't visible locally, using HEVC might give YouTube's encoder a better starting point.
   • Upload videos in formats and resolutions recommended by YouTube.​
   • Be aware that platforms like YouTube apply their own compression, which can affect video quality.
   • Slight Noise/Grain: Sometimes adding a very subtle amount of film grain or noise during editing (using an effect) can help break up smooth gradients that compression algorithms struggle with, potentially masking the banding. This is more of a workaround.
8. Other points to consider:
   • Smart HDR: This feature adjusts brightness and contrast automatically, but it might not always produce desirable results. Try disabling Smart HDR during export to see if it affects the appearance of the yellowish lines.
   • Noise Reduction and Voice Tone Change: While these features aim to enhance audio quality, they can sometimes introduce distortions. Consider turning them off during export to check for improvements.
   • If your source clips are of low quality or have inherent issues, these can be exacerbated during editing and export. Ensure your original footage is of high quality and free from defects before importing it into CapCut.

Recommendation:

Start by checking the local exported file (Step 1). Then, focus on changing the container to MP4 (Step 2) and disabling hardware acceleration (Step 3) as your first tests, exporting short problematic clips each time to save time. If those don't work, proceed through the other export setting variations and software checks. Good luck!

By systematically adjusting these settings and considerations, you should be able to identify and resolve the issue causing the yellowish lines in your exported videos.