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refactor(web): add runtime audio encoder capability negotiation for mp4 exports #757

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refactor(web): add runtime audio encoder capability negotiation for mp4 exports #757

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45 changes: 45 additions & 0 deletions apps/web/src/lib/export/audio-codec-support.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
const CANDIDATE_CONFIGS: AudioEncoderConfig[] = [
{
codec: "mp4a.40.2",
sampleRate: 44100,
numberOfChannels: 2,
bitrate: 192000,
},
{
codec: "mp4a.40.2",
sampleRate: 44100,
numberOfChannels: 2,
bitrate: 128000,
},
{
codec: "mp4a.40.2",
sampleRate: 44100,
numberOfChannels: 1,
bitrate: 128000,
},
{
codec: "mp4a.40.2",
sampleRate: 48000,
numberOfChannels: 2,
bitrate: 128000,
},
];

export async function resolveSupportedMp4AudioConfig(): Promise<AudioEncoderConfig | null> {
if (typeof AudioEncoder === "undefined") {
return null;
}

for (const config of CANDIDATE_CONFIGS) {
try {
const support = await AudioEncoder.isConfigSupported(config);
if (support.supported) {
return config;
}
} catch {
continue;
}
}

return null;
}
Comment on lines +28 to +45
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@coderabbitai coderabbitai bot Apr 2, 2026

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⚠️ Potential issue | 🟠 Major

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Verify helper adoption and detect remaining hardcoded probing in exporter flow.

set -euo pipefail

echo "== locate new helper usages =="
rg -nP --type=ts '\bresolveSupportedMp4AudioConfig\s*\(' -C2

echo
echo "== locate direct AudioEncoder probing still in renderer/export paths =="
rg -nP --type=ts '\bAudioEncoder\.isConfigSupported\s*\(' -C3 apps/web/src/services/renderer/scene-exporter.ts apps/web/src/lib/export/audio-codec-support.ts || true

echo
echo "Expected:"
echo "1) scene-exporter path references resolveSupportedMp4AudioConfig()."
echo "2) hardcoded AAC probe logic is removed or delegated to the utility."

Repository: OpenCut-app/OpenCut

Length of output: 1930

Integrate the new helper into the MP4 export path.

The resolveSupportedMp4AudioConfig() function is defined but never called. scene-exporter.ts (lines 107–110) still contains the hardcoded AAC probe logic that should delegate to this utility:

const { supported } = await AudioEncoder.isConfigSupported({
    codec: "mp4a.40.2",
    sampleRate: this.audioBuffer.sampleRate,
    numberOfChannels: this.audioBuffer.numberOfChannels,

Replace this with resolveSupportedMp4AudioConfig() to centralize codec negotiation and achieve the PR's runtime-fallback objective.

🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@apps/web/src/lib/export/audio-codec-support.ts` around lines 28 - 45, Replace
the hardcoded AAC probe in the MP4 export flow with the new helper: call
resolveSupportedMp4AudioConfig() from the export logic (the place currently
calling AudioEncoder.isConfigSupported with codec "mp4a.40.2" and
sampleRate/numberOfChannels) and use the returned AudioEncoderConfig (or null)
instead of the inline probe; if it returns null, proceed with the existing
fallback/no-audio path. Update the code path that currently expects { supported
} from AudioEncoder.isConfigSupported to await resolveSupportedMp4AudioConfig()
and branch on its result so codec negotiation is centralized.