Replace Audio not working

[jauling]

The fewer issues I have to read, the more new features I will have time to implement, so I ask that you please try these things first

• Try with the newest version from GitHub (also it might have already been fixed in latest nightly build)
• Read the documentation and FAQ, Known issues, Troubleshooting
• Search for your problem under Issues or Discussions
• This problem happens with all kinds of files that I try. For problem only with a particular file or type, use this other form instead

Operating System

MacOS 15

Steps to reproduce

I'm trying to replace the audio track of a mp4 video that was exported from Insta360 Studio.

1. I first opened the mp3 music file in LosslessCut, and trimmed it down to the segment I want. I then exported it successfully.
2. I then add the video track and disable its associated audio track. Files are slightly different lengths so I select "Shortest".
3. Export

I've also tried closing LosslessCut, opening the video file first, then adding the audio file, disabling the audio track of the video file, and exporting. I've also tried selecting "Longest" for output file length.

Input audio ffmpeg info:

  Duration: 00:01:00.03, start: 0.011995, bitrate: 320 kb/s
  Stream #0:0: Audio: mp3 (mp3float), 44100 Hz, stereo, fltp, 320 kb/s
      Metadata:
        encoder         : LAME3.99r
      Side data:
        replaygain: track gain - -4.200000, track peak - unknown, album gain - unknown, album peak - unknown,

Input video ffmpeg info:

  Duration: 00:01:00.02, start: 0.000000, bitrate: 20132 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709, progressive), 1080x1920, 25072 kb/s, 29.97 fps, 29.97 tbr, 30k tbn (default)
      Metadata:
        creation_time   : 2025-01-08T11:29:10.000000Z
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](und): Audio: mp3 (mp3float) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 320 kb/s (default)
      Metadata:
        creation_time   : 2025-01-08T11:29:10.000000Z
        handler_name    : SoundHandler
        vendor_id       : [0][0][0][0]

Expected behavior

Can hear audio!

Actual behavior

No audio.

Output file ffmpeg info:

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'VID_20250108_132920_00_002(sunkissed)-00.00.00.000-00.00.57.424.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 2025-01-08T11:29:10.000000Z
    encoder         : Lavf60.3.100
  Duration: 00:01:00.02, start: 0.000000, bitrate: 20132 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709, progressive), 1080x1920, 25072 kb/s, 29.97 fps, 29.97 tbr, 30k tbn (default)
      Metadata:
        creation_time   : 2025-01-08T11:29:10.000000Z
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](und): Audio: mp3 (mp3float) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 320 kb/s (default)
      Metadata:
        creation_time   : 2025-01-08T11:29:10.000000Z
        handler_name    : SoundHandler
        vendor_id       : [0][0][0][0]

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