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import { Input, ALL_FORMATS, BlobSource } from "mediabunny";
import { createTimelineAudioBuffer } from "@/media/audio";
import type { SceneTracks } from "@/timeline";
import type { MediaAsset } from "@/media/types";
import { TICKS_PER_SECOND } from "@/wasm";
export async function getVideoInfo({
videoFile,
}: {
videoFile: File;
}): Promise<{
duration: number;
width: number;
height: number;
fps: number;
hasAudio: boolean;
}> {
const input = new Input({
source: new BlobSource(videoFile),
formats: ALL_FORMATS,
});
const duration = await input.computeDuration();
const videoTrack = await input.getPrimaryVideoTrack();
if (!videoTrack) {
throw new Error("No video track found in the file");
}
const packetStats = await videoTrack.computePacketStats(100);
const fps = packetStats.averagePacketRate;
const audioTrack = await input.getPrimaryAudioTrack();
return {
duration,
width: videoTrack.displayWidth,
height: videoTrack.displayHeight,
fps,
hasAudio: audioTrack !== null,
};
}
const SAMPLE_RATE = 44100;
const NUM_CHANNELS = 2;
const EMPTY_TIMELINE_SILENT_DURATION_SECONDS = 0.1;
const MIN_SILENT_DURATION_SECONDS = 0.001;
export const extractTimelineAudio = async ({
tracks,
mediaAssets,
totalDuration,
onProgress,
}: {
tracks: SceneTracks;
mediaAssets: MediaAsset[];
totalDuration: number;
onProgress?: (progress: number) => void;
}): Promise<Blob> => {
if (totalDuration === 0) {
return createWavBlob({
samples: new Float32Array(
SAMPLE_RATE * EMPTY_TIMELINE_SILENT_DURATION_SECONDS,
),
});
}
onProgress?.(10);
const audioBuffer = await createTimelineAudioBuffer({
tracks,
mediaAssets,
duration: totalDuration,
sampleRate: SAMPLE_RATE,
});
if (!audioBuffer) {
const silentDurationSeconds = Math.max(
MIN_SILENT_DURATION_SECONDS,
totalDuration / TICKS_PER_SECOND,
);
const silentSamples = new Float32Array(
Math.ceil(silentDurationSeconds * SAMPLE_RATE) * NUM_CHANNELS,
);
return createWavBlob({ samples: silentSamples });
}
onProgress?.(90);
const interleavedSamples = interleaveAudioBuffer({ audioBuffer });
onProgress?.(100);
return createWavBlob({ samples: interleavedSamples });
};
function interleaveAudioBuffer({
audioBuffer,
}: {
audioBuffer: AudioBuffer;
}): Float32Array {
const numChannels = Math.min(NUM_CHANNELS, audioBuffer.numberOfChannels);
const interleavedSamples = new Float32Array(
audioBuffer.length * NUM_CHANNELS,
);
for (let sampleIndex = 0; sampleIndex < audioBuffer.length; sampleIndex++) {
for (let channel = 0; channel < NUM_CHANNELS; channel++) {
const sourceChannel = Math.min(channel, Math.max(0, numChannels - 1));
interleavedSamples[sampleIndex * NUM_CHANNELS + channel] =
audioBuffer.getChannelData(sourceChannel)[sampleIndex] ?? 0;
}
}
return interleavedSamples;
}
function createWavBlob({ samples }: { samples: Float32Array }): Blob {
const numChannels = NUM_CHANNELS;
const bitsPerSample = 16;
const bytesPerSample = bitsPerSample / 8;
const numSamples = samples.length / numChannels;
const dataSize = numSamples * numChannels * bytesPerSample;
const buffer = new ArrayBuffer(44 + dataSize);
const view = new DataView(buffer);
// riff header
writeString({ view, offset: 0, str: "RIFF" });
view.setUint32(4, 36 + dataSize, true);
writeString({ view, offset: 8, str: "WAVE" });
// fmt chunk
writeString({ view, offset: 12, str: "fmt " });
view.setUint32(16, 16, true);
view.setUint16(20, 1, true);
view.setUint16(22, numChannels, true);
view.setUint32(24, SAMPLE_RATE, true);
view.setUint32(28, SAMPLE_RATE * numChannels * bytesPerSample, true);
view.setUint16(32, numChannels * bytesPerSample, true);
view.setUint16(34, bitsPerSample, true);
// data chunk
writeString({ view, offset: 36, str: "data" });
view.setUint32(40, dataSize, true);
// convert float32 to int16 and write
let offset = 44;
for (let i = 0; i < samples.length; i++) {
const sample = Math.max(-1, Math.min(1, samples[i]));
const int16 = sample < 0 ? sample * 0x8000 : sample * 0x7fff;
view.setInt16(offset, int16, true);
offset += 2;
}
return new Blob([buffer], { type: "audio/wav" });
}
function writeString({
view,
offset,
str,
}: {
view: DataView;
offset: number;
str: string;
}): void {
for (let i = 0; i < str.length; i++) {
view.setUint8(offset + i, str.charCodeAt(i));
}
}
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