Different file sizes after export on different laptops

Hi,

It is perplexing that, despite using identical export settings, input files, and CapCut versions, your exported video is approximately 1.45 GB, while your team member's is over 6 GB. Several factors could contribute to this discrepancy:

1. Hardware Differences: Variations between your Acer and HP laptops, such as different graphics cards or processors, might influence the encoding process, potentially leading to differences in file sizes.

   • CPU and GPU: Different processors and graphics cards from Intel, AMD, or NVIDIA.
   • Video Encoders: Modern CPUs and GPUs often have dedicated hardware video encoders (like Intel Quick Sync Video, NVIDIA NVENC, AMD VCE). CapCut would utilize these hardware encoders for faster export. Even if you select the "software" encoder option, the underlying software encoder implementations might still vary slightly between different systems.
   • Operating System and Drivers: Differences in operating system versions (Windows versions, etc.) and the specific versions of graphics drivers installed on each laptop could also lead to subtle variations in how the video encoding process is handled.

2. Hidden Setting Variations: Even with the same visible export settings, there might be underlying configurations or defaults that differ between your installations.

3. Source File Properties: Ensure that both of you are indeed using the exact same source file. Differences in file properties, even if subtle, can affect the final output size.

   • "Same Input File" - Verify Absolutely Identical: Double-check that the source video file used by both of you is byte-for-byte identical. Even if they appear visually the same, subtle differences in the original encoding, metadata, or file container could exist. Compare file hashes or checksums if you want to be absolutely certain.
   • Edit Variations: While you describe minimal edits (cuts and loudness normalization), ensure that the cuts are exactly at the same frames in both projects. Even a few frames difference in cut points could slightly alter the overall video complexity and encoding.
   • Loudness Normalization Implementation: While loudness normalization is a minimal edit, different software or even slightly different implementations of loudness normalization could theoretically lead to minor variations in the audio encoding, though this is less likely to explain a large file size difference.

4. Software Glitches: Occasionally, software anomalies can cause unexpected results.

   • System-Specific Conflicts: There could be some other software or driver conflict on one of the laptops that is indirectly affecting CapCut's encoding process.

5. Variable Bitrate (VBR) Encoding:

   • CapCut, uses Variable Bitrate (VBR) encoding by default. VBR dynamically adjusts the bitrate (data rate) of your video based on the complexity of the content at any given moment.
   • Complexity Matters: Scenes with more motion, detail, and changes require a higher bitrate to maintain quality. Scenes with less complexity (e.g., static shots, talking heads) can use a lower bitrate.
   • Why File Sizes Differ: Even if you set the same target bitrate, if the content of your team member's video export is deemed more "complex" by the encoder (even subtly), VBR encoding could result in a significantly higher average bitrate over the entire video, leading to a larger file size. This could happen even if the visual differences in complexity are not immediately obvious to the human eye.
6. File size estimation inaccuracy: As you noted, the "Estimated File Size" in CapCut is just an estimation. It's not always perfectly accurate, especially with VBR encoding. The fact that both of your actual exported file sizes are significantly different from the estimation is interesting, but the relative difference between your export and your team member's export is the key issue.

Recommendations:

• Verify Source Files: Double-check that both of you are using identical source files by comparing their properties.

  • Carefully compare every single setting in your export windows, pixel by pixel, against your team member's settings in the screenshot. Even small, seemingly insignificant differences can sometimes matter.
  • Specifically confirm:
    • Resolution: (e.g., 2560x1440)
    • Frame Rate: (e.g., 30)
    • Format: (MP4 is likely)
    • Codec: (If CapCut allows codec selection, ensure it's the same)
    • Bitrate Settings: (Crucially, verify the exact bitrate value set. Is it "Custom Bitrate" or a "Quality" setting? If "Custom," what is the Kbps or Mbps value? If "Quality," is the quality level slider set to the same position?)
    • Audio Settings: (Codec, Bitrate, Sample Rate - if adjustable)

• Experiment with Bitrate Settings - Lower Bitrate for Smaller Files:

  • Reduce Bitrate: The most direct way to reduce file size is to lower the bitrate in your export settings. If you are using a "Custom Bitrate," try reducing the Kbps or Mbps value. If you are using a "Quality" slider, move the slider to a lower quality setting.
  • Test Export at Lower Bitrates: Export a short test clip at several different bitrate settings (e.g., try reducing the bitrate by 20%, 40%, 60% increments). Compare the resulting file sizes and visually assess the video quality at each bitrate. Find the lowest bitrate that still provides acceptable video quality for your course content. This will give you the smallest possible file size while maintaining reasonable quality.
  • Consider Constant Bitrate (CBR) - If Available: Check if there is an option to switch from Variable Bitrate (VBR) to Constant Bitrate (CBR) encoding. CBR forces the encoder to use a consistent bitrate throughout the video. CBR can sometimes result in slightly larger file sizes than VBR for the same average quality, but it can also lead to more predictable file sizes. However, CapCut might not expose CBR/VBR settings to the user.

• Test with a Short, Simple "Control" Video:

  • Create a Very Short Test: In CapCut, create a new, very short project (e.g., just 10-20 seconds long). Use a simple source – like a screen recording of a static image, or just a few seconds of plain color bars generated within CapCut itself (if possible). The goal is to have very minimal video complexity.
  • Export with Identical Settings: Export this short, simple test video on both your Acer and your team member's HP laptop using the exact same export settings (the settings from your screenshot).
  • Compare File Sizes: Compare the exported file sizes of this simple test video. If the file sizes are now much closer or nearly identical, it suggests that the file size difference is related to the complexity of your actual course video content and VBR encoding. If the file sizes are still drastically different even with a simple test video, it points more towards a system-specific or software bug issue.

• Compare Estimated File Sizes Before Export:

  • Note Estimated Sizes: Before you start the actual export process on both laptops, carefully note down the "Estimated File Size" that CapCut displays in the export window for the same project and same export settings.
  • Compare Estimations: If the estimated file size is already drastically different before exporting, this strongly indicates that CapCut is calculating the file size estimation differently on each system, which could also be related to the underlying encoding process.

• Check Source File Properties in Detail:

  • Right-Click -> Properties (Windows) or Get Info (Mac): On both laptops, right-click on the original source video file (before importing into CapCut) and go to "Properties" (Windows) or "Get Info" (Mac).
  • Compare Detailed Properties: Carefully compare all the technical details listed, including:
    • File Size (of the source file itself)
    • Resolution
    • Frame Rate
    • Video Codec
    • Audio Codec
    • Duration
    • Bitrate (if available in file properties)
  • Ensure 100% Identical Source: Confirm that all of these properties are absolutely identical for the source file on both laptops. If there are any differences, even minor ones, it could contribute to encoding variations.

• Experiment with Different Export Formats/Codecs:

  • Format Options: Try different export formats beyond MP4 (e.g., MOV, AVI - though MP4 is standard for web). If so, try exporting in a different format as a test to see if it changes file size behavior.
  • Codec Options: CapCut might or might not expose options to select specific video codecs (like H.264, HEVC/H.265, etc.) or audio codecs (AAC, MP3, etc.). If you do see codec selection options in the export settings, try experimenting with different codecs to see if it impacts file size consistency. However, CapCut often simplifies the interface and may not give direct codec control.

• Reinstall CapCut: Consider reinstalling CapCut on both machines to ensure a clean setup.

• Test on a Different Machine: Try exporting the project on a third computer to see if the issue persists.

• Lower Resolution as a Last Resort (If Quality is Less Critical):

  • Reduce Resolution: If file size is the absolute priority to fit your course platform's 2GB limit, and if some quality reduction is acceptable, consider exporting at a slightly lower resolution than your current setting. For example, if you are exporting at 1440p, try exporting at 1080p. Lower resolution directly reduces the amount of data needed to represent each frame, thus reducing file size.
• File Compression Tools (As a Post-Export Workaround): As a temporary workaround to meet your 2GB limit after exporting from CapCut, you could use separate video compression software to further reduce the file size of the larger 6GB export. However, this is an extra step and may slightly reduce quality further. Tools like HandBrake (free and open-source) are commonly used for video compression. But ideally, you want to solve the issue within CapCut export itself.

• Contact Support: If the problem continues, reaching out to CapCut's support team at [email protected] might provide more specialized assistance. Explain the problem in detail, providing screenshots of your export settings and describing the troubleshooting steps you've taken. They may be able to provide more specific guidance or identify if there's a bug in their software.

Understanding that video file sizes are influenced by factors like frame rate, bit rate, resolution, duration, and codecs is crucial. Even minimal differences in these parameters can lead to significant variations in file sizes.

Lowering the bitrate in your export settings is the most effective way to directly reduce your exported video file size. Experiment with lower bitrates until you find a balance between file size and acceptable video quality for your course content.

By systematically investigating these areas, you can identify the root cause of the discrepancy and ensure consistent export results across different devices.