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?
(I have updated the version from the earlier one to 23.08.04; on my machine as well as in the bug report) In conjunction with the other bugs that I had to report, and Bernd's suggestion to try "Audio only", I'd like to update, that there is still a logical as well as processing bug. When I disable the "Video" in the Render applet, the Job Queue states below the thermometer "Audio without video track". Fine, but why would any of the separate "..._Audio_..." tracks be WITH a video track; whatever one selects at the "Video" box? (Better try yourself, if I'm not very clear here, or ask, please.) In any case, the rendering speed of the audio tracks increases, when "Video" is ticked, by close to half of what audio rendering takes with "Video" being ticked. It remains completely unclear, why a pure "..._Audio_..." track renders significantly faster when no video track needs rendering at an earlier or later moment in time? In any case, even without "Video" being ticked, rendering of the EACH audio track takes around one third of rendering the H264 video track. Next, I followed Bernd's suggestion, and selected "Audio Only" Presets for rendering. I tries AC3 as well as MP3. Unfortunately, neither is any faster than around one third of rendering the video track. On this machine, rendering a 2-hour video track takes around 4 hours. An audio track with "Video" ticked, is around 2 hours. An audio track without "Video" ticked takes about an hour; either as .mp4; or .ac3 or .mp3 (the letter two with "Audio Only" presets. On that same machine, Audacity takes about 5 minutes to render that 2-hour audio track; with a similar size of the output file, around 130 MB. (I don't want to write another bug report for the lack of logic for this:) With "Audio Only" presets, "Video" can still be ticked, however. I haven't tried to see what kdenlive does with this setting, in order to keep my sanity. ;-)
Git commit 4345933ca67ee473f22d11f90b47032c50f2895b by Jean-Baptiste Mardelle. Committed on 08/08/2024 at 06:12. Pushed by mardelle into branch 'release/24.08'. Make audio only render faster When using separate audio files render and exporting in a video format, switch audio file rendering to WAV M +4 -4 data/profiles.xml M +20 -10 src/dialogs/renderwidget.cpp M +28 -8 src/render/renderrequest.cpp https://invent.kde.org/multimedia/kdenlive/-/commit/4345933ca67ee473f22d11f90b47032c50f2895b