Mix Video with vocal audio and music audio using ffmpeg

SlimScreenRecordTabFragment.java

package com.arthenica.ffmpegkit.test;

import static com.arthenica.ffmpegkit.test.MainActivity.TAG;
import static com.arthenica.ffmpegkit.test.MainActivity.notNull;

import android.os.Bundle;
import android.os.Environment;
import android.text.method.ScrollingMovementMethod;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import com.arthenica.ffmpegkit.FFmpegKit;
import com.arthenica.ffmpegkit.ReturnCode;

import java.io.File;

public class SlimScreenRecordTabFragment extends Fragment {

    private static final String VOCAL_AUDIO_URL = "https://example.com/audio/vocal.mp3";
    private static final String MUSIC_AUDIO_URL = "https://example.com/audio/music.mp3";
    private static final String VIDEO_FILE_NAME = "record-1667288804378.ts";
    private TextView outputText;

    public static SlimScreenRecordTabFragment newInstance() {
        return new SlimScreenRecordTabFragment();
    }

    public SlimScreenRecordTabFragment() {
        super(R.layout.fragment_slim_screen_record_tab);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        Button runButton = view.findViewById(R.id.runButton);
        runButton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                runTest();
            }
        });

        outputText = view.findViewById(R.id.outputText);
        outputText.setMovementMethod(new ScrollingMovementMethod());
    }

    private void runTest() {
        clearOutput();

        final File sdcardRoot = Environment.getExternalStorageDirectory();
        final String inVideoPath = new File(sdcardRoot, VIDEO_FILE_NAME).getAbsolutePath();
        final String outVideoPath = new File(sdcardRoot, "out.mp4").getAbsolutePath();

        final String ffmpegCommand = String.format("-hide_banner -y "
                + "-i \"%s\" "
                + "-i \"%s\" "
                + "-i \"%s\" "
                + "-filter_complex \"[1:a][2:a]amix=inputs=2:duration=longest:dropout_transition=0:weights='1 0.5':normalize=0[a]\" "
                + "-map \"0:v\" -map \"[a]\" "
                + "-c:v \"copy\" -c:a \"aac\" "
                + "-f \"mp4\" \"%s\"", inVideoPath, VOCAL_AUDIO_URL, MUSIC_AUDIO_URL, outVideoPath);

        Log.d(TAG, String.format("FFmpeg process started with arguments: '%s'.", ffmpegCommand));
        FFmpegKit.executeAsync(ffmpegCommand, session -> {
            Log.d(TAG, String.format("FFmpeg process exited with state %s and rc %s.%s", session.getState(),
                    session.getReturnCode(), notNull(session.getFailStackTrace(), "\n")));

            MainActivity.addUIAction(() -> {
                if (ReturnCode.isSuccess(session.getReturnCode())) {
                    Popup.show(requireContext(), "ffmpeg completed successfully.");
                } else {
                    Popup.show(requireContext(), "ffmpeg failed. Please check logs for the details.");
                }
            });
        }, log -> MainActivity.addUIAction(() -> {
            appendOutput(log.getMessage());
        }), statistics -> {
            Log.d(TAG, statistics.toString());
        });
    }

    public void appendOutput(final String logMessage) {
        outputText.append(logMessage);
    }

    public void clearOutput() {
        outputText.setText("");
    }
}

video_audio_mixer.sh

# command on desktop

ffmpeg \
-i <video mp4> \
-i <vocal mp3> \
-i <background music mp3> \
-filter_complex "[1:a][2:a]amix=inputs=2:duration=longest:dropout_transition=0:weights='1 0.5':normalize=0[a]" \
-map "0:v" -map "[a]" \
-c:v "copy" -c:a "aac" \
-f "mp4" "out.mp4"


# see:
# - https://stackoverflow.com/questions/14498539/how-to-overlay-downmix-two-audio-files-using-ffmpeg
# - https://blog.nytsoi.net/2017/12/31/ffmpeg-combining-audio-tracks
# - https://gist.github.com/LukasKnuth/4d7ee6812ccb221b2775e984516b56d4

4分12 秒 1080p 30fps 视频，文件大小：107M
ffmpeg 处理耗时：15秒，CPU 占用：100%（即把一核占满），内存 约1%