android - FFmpeg adding image watermark to video process is very slow

Question

I am adding image watermark to video with help of FFmpeg but FFmpeg takes an inordinate amount of time with the below command-

String[] cmd = {"-i",videoPath, "-i", waterMark.toString(),"-filter_complex","overlay=5:5","-codec:a", "copy", outputPath};

so i tried another command which was little bit faster but increase output file size(which i do not want)

String[] cmd = {"-y","-i", videoPath, "-i", waterMark.toString(), "-filter_complex", "overlay=5:5", "-c:v","libx264","-preset", "ultrafast", outputPath};

Some one please explain to me how to increase the speed of FFmpeg watermarking speed without increasing the size of output. Thanks.

Answer 1

You mentioned that a 7MB video takes between 30-60 seconds.

There is always a trade off when choosing between speed and quality.

I tested on my phone using a 7MB file and it took 13 seconds, still slow, but we can't expect much better then that.

Ways to increase speed:

• Lowering the frame rate, using the -r command
• Changing the bitrate, using the -b:v and -b:a commands
• Change the Constant Rate Factor, using -crf. The default value is 21

The range of the quantizer scale is 0-51: where 0 is lossless, 23 is default, and 51 is worst possible. A lower value is a higher quality and a subjectively sane range is 18-28. Consider 18 to be visually lossless or nearly so: it should look the same or nearly the same as the input but it isn't technically lossless.

This is what I have found works the best on most android devices:

String[] s = {"-i", VideoPath, "-i", ImagePath, "-filter_complex", "[0:v]pad=iw:if(lte(ih\,iw)\,ih\,2*trunc(iw*16/9/2)):(ow-iw)/2:(oh-ih)/2[v0];[1:v][v0]scale2ref[v1][v0];[v0][v1]overlay=x=(W-w)/2:y=(H-h)/2[v]", "-map", "[v]", "-map", "0:a", "-c:v", "libx264", "-preset", "ultrafast", "-r", myFrameRate, directoryToStore[0] + "/" + SavedVideoName};

I reduced my framerate slightly, you can experiment what works best for you. I'm using mp4parser to retrieve the frame rate.

I have to give credit to @Gyan that provided me with a way to perfectly scale images that is being placed on top of a video, you can look at the question I asked here.

If you are unsure about the frame rate, you can remove it from the command and first test if your speed is reduced.

Try it, if you have any questions, please ask.

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OP opted to go with the following command:

String[] cmd = {"-y","-i", videoPath, "-i", waterMark.toString(), "-filter_complex", "overlay=(main_w-overlay_w-10):5", "-map", "0:a","-c:v", "libx264", "-crf", "28","-preset", "ultrafast" ,outputPath};

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Edit

Just to add on the command I mentioned and provide a detailed explanation of how to use it etc:

String[] cmd = {"-i", videoPath, "-i", waterMark.toString(), "-filter_complex", "[0:v]pad=iw:if(lte(ih\,iw)\,ih\,2*trunc(iw*16/9/2)):(ow-iw)/2:(oh-ih)/2[v0];[1:v][v0]scale2ref[v1][v0];[v0][v1]overlay=x=(W-w)/2:y=(H-h)/2[v]", "-map", "[v]", "-map", "0:a", "-c:v", "libx264", "-preset", "ultrafast", "-r", myFrameRate, outputPath};

This is for device's that has a display aspect ratio of 16:9. If you want this filter to work on all device's you will have to get the aspect ratio of the device and change the filter 16/9/2 respectively.

You can get the device aspect ratio by creating this methods:

int gcd(int p, int q) { 
    if (q == 0) return p; 
    else return gcd(q, p % q); 
} 
void ratio(int a, int b) { 
    final int gcd = gcd(a,b); 
    if(a > b) { 
        setAspectRatio(a/gcd, b/gcd); 
    } else { 
        setAspectRatio(b/gcd, a/gcd); 
    } 
} 
void setAspectRatio(int a, int b) { 
    System.out.println("aspect ratio = "+a + " " + b); 
    //This is the string that will be used in the filter (instead of hardcoding 16/9/2
    filterAspectRatio = a + "/" + b + "/" + "2"; 
}

Now you have the correct aspect ratio and you can change the filter accordingly.

Next, create a watermark and add it to a view, make that view the size of the device (match_parent) and scale/place the watermark where you would like it to be. You can then get the bitmap by calling:

Bitmap waterMarkBitmap = watermarkView.getDrawingCache();

and create a file from the Bitmap, like this:

String outputFilename = "myCoolWatermark.png"; //provide a name for you saved watermark
File path = Environment.getExternalStorageDirectory(); //this can be changed to where you want to store the bitmap
File waterMark = new File(path, outputFilename); 

try (FileOutputStream out = new FileOutputStream(waterMark)) { 
    waterMarkBitmap.compress(Bitmap.CompressFormat.PNG, 100, out); // PNG is a lossless format, the compression factor (100) is ignored 
} catch (IOException e) { 
    e.printStackTrace(); 
}

The watermark is created and can be reused, or you can delete it when you are done with it.

Now you can call the command mentioned above.