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• Fix a duplicate word.

  11 février 2012, par Ralph Giles

  Fix a duplicate word.
  Thanks to darkstarbyte for pointing out the typo.
  git-svn-id : http://svn.xiph.org/trunk/theora@18195 0101bb08-14d6-0310-b084-bc0e0c8e3800
  

  • [DH] doc/spec/spec.tex

• avcodec/dca : fix sync word search error condition

  2 mai 2016, par foo86

  avcodec/dca : fix sync word search error condition
  This didn’t actually check if sync word was found and always errored out
  
  with "-err_detect explode" option enabled.
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/dca_core.c

• how to add effect to audio, sound like a phone call phone, inner monologue, or sounds like a man/woman ? [closed]

  7 mars, par Mathew

  I'm trying to apply different audio effects, such as making audio sound like a phone call. Below is my current approach. As you can see, I'm using multiple filters and simple algorithms to achieve this effect, but the output quality isn't ideal.

  


  I've looked into FFmpeg filters and noticed mentions of LADSPA/LV2 plugins. Are these viable solutions ? Any other suggestions would be greatly appreciated.

  


  public static void applySceneEffect(String inputPath, String outputPath, int sceneType) {
    LOGGER.info("apply scene effect {} to {}", sceneType, inputPath);

    try (FFmpegFrameGrabber grabber = new FFmpegFrameGrabber(inputPath);
         FFmpegFrameRecorder recorder = new FFmpegFrameRecorder(outputPath, grabber.getAudioChannels())) {

        grabber.setOption("vn", ""); 
        grabber.start();

       
        recorder.setAudioCodec(avcodec.AV_CODEC_ID_PCM_S16LE); 
        recorder.setSampleRate(grabber.getSampleRate());
        recorder.setAudioChannels(grabber.getAudioChannels());
        recorder.setAudioBitrate(grabber.getAudioBitrate());
        recorder.setFormat("wav"); 


        String audioFilter = String.join(",",
                "aresample=8000",      
                "highpass=f=300, lowpass=f=3400",       
                "acompressor=threshold=-15dB:ratio=4:attack=10:release=100", 
                "volume=1.5",          
                "aecho=0.9:0.4:10:0.6"
        );

        FFmpegFrameFilter f1 = new FFmpegFrameFilter(audioFilter, grabber.getAudioChannels());
        f1.setSampleRate(grabber.getSampleRate());
        f1.start();

        recorder.start();

        Random random = new Random();
        double noiseLevel = 0.02; 

   
        while (true) {
            var frame = grabber.grabFrame(true, false, true, true);
            if (frame == null) {
                break;
            }

            ShortBuffer audioBuffer = (ShortBuffer) frame.samples[0];
            short[] audioData = new short[audioBuffer.remaining()];
            audioBuffer.get(audioData);

            applyElectricNoise(audioData, grabber.getSampleRate());

            audioData = applyDistortion(audioData, 1.5, 30000);

            audioBuffer.rewind();
            audioBuffer.put(audioData);
            audioBuffer.flip();


            f1.push(frame); 
            Frame filteredFrame;
            while ((filteredFrame = f1.pull()) != null) {
                recorder.record(filteredFrame); 
            }
        }

        recorder.stop();
        recorder.release();
        grabber.stop();
        grabber.release();
    } catch (FrameGrabber.Exception | FrameRecorder.Exception | FFmpegFrameFilter.Exception e) {
        throw new RuntimeException(e);
    }
}


private static final double NOISE_LEVEL = 0.005; 
private static final int NOISE_FREQUENCY = 60;  

public static void applyElectricNoise(short[] audioData, int sampleRate) {
    Random random = new Random();

    
    for (int i = 0; i < audioData.length; i++) {
        double noise = Math.sin(2 * Math.PI * NOISE_FREQUENCY * i / sampleRate);

        double electricNoise = random.nextGaussian() * NOISE_LEVEL * Short.MAX_VALUE + noise;

        audioData[i] = (short) Math.max(Math.min(audioData[i] + electricNoise, Short.MAX_VALUE), Short.MIN_VALUE); 
    }
}

public static short[] applyTremolo(short[] audioData, int sampleRate, double frequency, double depth) {
    double phase = 0.0;
    double phaseIncrement = 2 * Math.PI * frequency / sampleRate;

    for (int i = 0; i < audioData.length; i++) {
        double modulator = 1.0 - depth + depth * Math.sin(phase); 
        audioData[i] = (short) (audioData[i] * modulator);

        phase += phaseIncrement;
        if (phase > 2 * Math.PI) {
            phase -= 2 * Math.PI;
        }
    }
    return audioData;
}

public static short[] applyDistortion(short[] audioData, double gain, double threshold) {
    for (int i = 0; i < audioData.length; i++) {
        double sample = audioData[i] * gain;

        if (sample > threshold) {
            sample = threshold;
        } else if (sample < -threshold) {
            sample = -threshold;
        }

        audioData[i] = (short) sample;
    }
    return audioData;
}