https://bugs.kde.org/show_bug.cgi?id=491109
Bug ID: 491109
Summary: Audio export consumes exorbitant times
Classification: Applications
Product: kdenlive
Version: 22.04.3
Platform: Ubuntu
OS: Linux
Status: REPORTED
Severity: minor
Priority: NOR
Component: Video Display & Export
Assignee: j...@kdenlive.org
Reporter: udip...@gmail.com
Target Milestone: ---
SUMMARY
Exporting ("Render") in “Separate file for each audio track” takes exorbitant
times for each track. In my sample file here, MP4, exporting one video track
and one (included) audio track, takes around 4 hours.
Splitting the audio track as “Separate file for each audio track” rendering the
video only takes about the same time, but the additional rendering of that
single, separate audio track takes also around 2 hours.
STEPS TO REPRODUCE
1. Take a 'normal' movie,
2. Render it “Separate file for each audio track”
OBSERVED RESULT
Rendering of the audio-only takes around half of the time of the complete,
unified, rendering process
EXPECTED RESULT
Rendering the audio is faster by light years
ADDITIONAL INFORMATION
As comparison to the two hours of rendering a single audio track (on this slow
box, agreed), here is what that same box takes outside of kde:
1. Extract the same audio stream (ac3) to an ac3-file: 90 seconds
2. Importing into Audacity: 50 seconds
3. Rendering to FLAC: 140 seconds
Therefore, the path over Audacity takes less than 5 minutes to obtain a similar
result, while kdenlive takes around 120 minutes.
This is only my suspicion: While rendering the audio-only, it still does
something with the video. ffprobe says:
Meetadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.76.100
Duration: 01:48:50.03, start: 0.000000, bitrate: 190 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709),
1280x720 [SAR 1:1 DAR 16:9], 19 kb/s, 50 fps, 50 tbr, 12800 tbn, 100 tbc
(default)
Metadata:
handler_name : VideoHandler
vendor_id : [0][0][0][0]
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo,
fltp, 160 kb/s (default)
Metadata:
handler_name : SoundHandler
vendor_id : [0][0][0][0]
Why is there a video stream?
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