使用 ffmpeg 将多个音频合并到视频会导致音量减小。如何避免这种情况？

Question

        const command = ffmpeg();

        const mp4Path = path.join(__dirname, '..', '..', 'temp', `q-video-${new Date().getTime()}.mp4`);

        fs.writeFileSync(mp4Path, videoBuff);
        console.log('mp4 file created at: ', mp4Path);

        // Set the video stream as the input for ffmpeg
        command.input(mp4Path);

        const mp3Paths = [];

        for (let i = 0; i < audios.length; i++) {
            const audio = audios[i];
            const mp3Path = path.join(__dirname, '..', '..', 'temp', `q-audio-${new Date().getTime()}-${i}.mp3`);
            mp3Paths.push(mp3Path);

            fs.writeFileSync(mp3Path, audio.questionBuf);
            console.log('mp3 file created at: ', mp3Path);
            // Set the audio stream as the input for ffmpeg
            command.input(mp3Path);
        }

        // -------
        // ChatGPT take 1
        const audioTags = [];
        const audioFilters = audios.map((audio, index) => {
            const startTime = audio.start_at; // Replace with your logic to calculate start time
            const endTime = audio.end_at;     // Replace with your logic to calculate end time
            audioTags.push(`[delayed${index}]`);
            // Working
            // return `[${index + 1}:a]atrim=start=0:end=${(endTime - startTime) / 1000},adelay=${startTime}[delayed${index}]`;
            return `[${index + 1}:a]dynaudnorm=p=0.9:m=100:s=5,atrim=start=0:end=${(endTime - startTime) / 1000},adelay=${startTime}[delayed${index}]`;
        });
        
        // Concatenate the delayed audio streams
        const concatFilter = audioFilters.join(';');
        
        // Mix the concatenated audio streams
        const mixFilter = `${concatFilter};[0:a]${audioTags.join('')}amix=inputs=${audios.length + 1}:duration=first:dropout_transition=2[out]`;

        // Set the complex filter for ffmpeg
        command.complexFilter([mixFilter]);

        // Set the output size
        if (!isScreen) {
            command.videoFilter('scale=720:-1');
        }
        else {
            command.videoFilter('scale=1920:-1');
        }

        // Set input options
        command.inputOptions([
            '-analyzeduration 20M',
            '-probesize 100M'
        ]);

        // Set output options
        command.outputOptions([
            '-c:v libx264', // Specify a video codec
            '-c:a aac',
            '-map 0:v',      // Map the video stream from the first input
            '-map [out]'     // Map the audio stream from the complex filter
        ]);

        // Set the output format
        command.toFormat('mp4');

        // Set the output file path
        command.output(outputFilePath);

        // Event handling
        command
            .on('start', commandLine => {
                console.log('Spawned Ffmpeg with command: ' + commandLine);
            })
            .on('codecData', data => {
                console.log('Input is ' + data.audio + ' audio ' +
                'with ' + data.video + ' video');
            })
            .on('progress', progress => {
                // console.log('progress: ', progress);
                console.log(`Processing: ${
                    progress.percent ?
                    progress.percent.toFixed(2)
                    :
                    '0.00'
                }% done`);
            })
            .on('stderr', stderrLine => {
                console.log('Stderr output: ' + stderrLine);
            })
            .on('error', (err, stdout, stderr) => {
                console.error('Error merging streams:', err);
                console.error('ffmpeg stdout:', stdout);
                console.error('ffmpeg stderr:', stderr);
                reject(err);
            })
            .on('end', () => {
                console.log('Merging finished successfully.');
                const file = fs.readFileSync(outputFilePath);
                console.log('File read successfully.');
                setTimeout(() => {
                    fs.unlinkSync(outputFilePath);
                    console.log('Output file deleted successfully.');
                    fs.unlinkSync(mp4Path);
                    console.log('MP4 file deleted successfully.');
                    console.log('mp3Paths: ', mp3Paths);
                    for (let mp3Path of mp3Paths) {
                        fs.unlinkSync(mp3Path);
                    }
                    console.log('MP3 file deleted successfully.');
                    if (isScreen) {
                        for (let path of pathsScreen) {
                            fs.unlinkSync(path);
                        }
                    }
                    else {
                        for (let path of pathsCamera) {
                            fs.unlinkSync(path);
                        }
                    }
                    console.log('All temp files deleted successfully.');
                }, 3000);
                resolve(file);
            });
        
        // Run the command
        command.run();

这就是我现在合并视频文件（这是一组 webm 文件）的方式。看来这个命令导致视频的音量从开始到结束逐渐增加（视频的早期部分的音量比视频的后期部分低得多）。我该如何解决这个问题？

到目前为止尝试和调查的事情：

• 我检查了原视频，没有音量问题。所以音量问题毫无疑问是由这段代码引起的。
• 我尝试过 dynaudnorm，但没有完全理解它是如何工作的。将其添加到每个音频文件并不能解决此问题，并且将其作为单独的过滤器添加到组合过滤器字符串的末尾会破坏会话。

Answer 1

我最终为问题中该命令生成的视频运行了另一个 ffmpeg 命令，它实际上有效并解决了我的问题。所以似乎没有办法在合并函数中运行它以使其按预期工作。