FFmpeg output seeking result to Android LruCache

问题

Dear fellow StackOverflower,

In my Android application, I'm trying to quickly retrieve a frame from a video using ffmpeg-android-java to display in an ImageView. The problem is using a typical ffmpeg's -ss seeking command will require to write the output into the memory which I suppose is the big hit on performance:

ffmpeg -ss 00:23:00 -i Mononoke.Hime.mkv -frames:v 1 out1.jpg

A typical command execution like above takes around 700 - 1200 milliseconds. So instead of writing into the memory, I would like to write it into LruCache hoping to achieve a better performance.

The problem is ffmpeg-android-java is a wrapper to execute ffmpeg command and as such I don't know how to correctly supply the LruCache's address for the command.

Below is my code snippet:

private void seekToPosition(long currentVideoPosition){

    String position = DiskUtils.formatMillisForFFmpeg(currentVideoPosition);

    String[] cmd = {"-ss", String.valueOf(position), "-i", mVideoPath,
                    "-y", "-an", "-frames:v", "1",
                    "/storage/emulated/0/Videos/out.jpg"}; //this the problem, I would like to change this to the address of LruCache

    try {
        // to execute "ffmpeg -version" command you just need to pass "-version"
        mFFmpeg.execute(cmd, new ExecuteBinaryResponseHandler() {

            long start;
            long end;

            @Override
            public void onStart() {
                canSeek = false;
                start = System.currentTimeMillis();
            }

            @Override
            public void onProgress(String message) {}

            @Override
            public void onFailure(String message) {
                Log.d(TAG, "FFmpeg cmd failure");
            }

            @Override
            public void onSuccess(String message) {
                Log.d(TAG, "FFmpeg cmd success");

                /*mFFmpeg.killRunningProcesses();
                Log.d(TAG, "FFmpeg kill running process: " + mFFmpeg.killRunningProcesses());*/
            }

            @Override
            public void onFinish() {
                canSeek = true;
                Log.d(TAG, "FFmpeg cmd finished: is FFmpeg process running: " + mFFmpeg.isFFmpegCommandRunning());
                end = System.currentTimeMillis();
                Log.d(TAG, "FFmpeg excuted in: " + (end - start) + " milliseconds");
            }
        });
    } catch (FFmpegCommandAlreadyRunningException e) {
        // Handle if FFmpeg is already running
        Log.d(TAG, "FFmpeg exception: " + e);
    }
} 

回答1:

To answer my own question, I haven't found the solution for this yet as it's kind of impossible in nature. So instead, I take the hard way of compiling the FFmpeg and using the JNI to use it as a library.

You can take a look at my step-by-step instructions if you need some guidance on building and using FFmpeg with Android Studio because I know trying to figure this out is a real nightmare.

Sorry I can't post all the instructions here as it is way too long, plus it is easier for me to keep 1 source of information up-to-date.

来源：https://stackoverflow.com/questions/37132546/ffmpeg-output-seeking-result-to-android-lrucache