[android-developers] Re: Modifying audio in real time
After calling play you need to keep calling write so you can feed AudioTrack´s internal buffer and keep the audio playing. Then, before you call read you can process your stream the way you want. About upsampling, downsamplig: it´s a tecnique for changing the samplerate of a signal trying to modify it as little as possible. When you downsample you lose information; when you upsample you interpolate to try to figure out what the information would be since you dont have it. For example, if you have a stream sampled at 10khz and want to downsample it to 5khz (which will play faster at your AudioTrack 10khz object) you just need to use the even or odd samples, and discard the rest. Hope it helps, Gabriel On 26 mar, 08:57, Simone Russo simone.russ...@gmail.com wrote: Hi, thank you very much for your answer. The problem I have is that I got an audio stream, say 5 seconds long. I want the user to be able to change the volume and the playbackrate while the sound is being played. I'm able to modify those parameters before i call the play() method, but I need to change them while the stream is being played as well What do you mean by you can upsample/downsample your streams to get the desired efect? Thanks again Simone 2010/3/26 Gabriel Simões gsim...@gmail.com Hello Simone. What problems have you been facing with AudioTrack? Besides the fact that you will need to handle all the overhead of time/ streams controling everything should work fine with AudioTrack, even using the Emulator. For the volume change for example, try to each position of your audio streams for a float between 0.0f (no sound) and 1.0f (volume at 100%) and cast back to short before playing. Should give you the results you want. For the SampleRate, once AudioTrack is created you cannot change it´s samplerate value, but you can upsample/downsample your streams to get the desired efect. Hope it helps, Gabriel On 23 mar, 17:57, Simone simone.russ...@gmail.com wrote: Hi everyone, I'll try to explain briefly what I need to do. I need to load an audio resource and play it, but I also need to be able to modify some parameters (like the volume, or the playback rate) while the audio is being played. For example, I might want to play a 10 seconds audio stream, and change the volume only after 3 seconds. Is there a way to do it? I've been experimenting a little with AudioTrack without results. Thanks, Simone -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.comandroid-developers%2bunsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en To unsubscribe from this group, send email to android-developers+ unsubscribegooglegroups.com or reply to this email with the words REMOVE ME as the subject.- Ocultar texto das mensagens anteriores - - Mostrar texto das mensagens anteriores - -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en To unsubscribe from this group, send email to android-developers+unsubscribegooglegroups.com or reply to this email with the words REMOVE ME as the subject.
Re: [android-developers] Re: Modifying audio in real time
Hi, thank you very much for your answer. The problem I have is that I got an audio stream, say 5 seconds long. I want the user to be able to change the volume and the playbackrate while the sound is being played. I'm able to modify those parameters before i call the play() method, but I need to change them while the stream is being played as well What do you mean by you can upsample/downsample your streams to get the desired efect? Thanks again Simone 2010/3/26 Gabriel Simões gsim...@gmail.com Hello Simone. What problems have you been facing with AudioTrack? Besides the fact that you will need to handle all the overhead of time/ streams controling everything should work fine with AudioTrack, even using the Emulator. For the volume change for example, try to each position of your audio streams for a float between 0.0f (no sound) and 1.0f (volume at 100%) and cast back to short before playing. Should give you the results you want. For the SampleRate, once AudioTrack is created you cannot change it´s samplerate value, but you can upsample/downsample your streams to get the desired efect. Hope it helps, Gabriel On 23 mar, 17:57, Simone simone.russ...@gmail.com wrote: Hi everyone, I'll try to explain briefly what I need to do. I need to load an audio resource and play it, but I also need to be able to modify some parameters (like the volume, or the playback rate) while the audio is being played. For example, I might want to play a 10 seconds audio stream, and change the volume only after 3 seconds. Is there a way to do it? I've been experimenting a little with AudioTrack without results. Thanks, Simone -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.comandroid-developers%2bunsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en To unsubscribe from this group, send email to android-developers+ unsubscribegooglegroups.com or reply to this email with the words REMOVE ME as the subject. -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en To unsubscribe from this group, send email to android-developers+unsubscribegooglegroups.com or reply to this email with the words REMOVE ME as the subject.
[android-developers] Re: Modifying audio in real time
To get a response in 'real time', you need to hear the volume change within 100ms or so of hitting the volume adjust picker or spinner or whatever. 8000 samples a sec is 8 samples in a ms, so if you process 800 sample chunks of the stream and shift each sample it left or right a bit to raise or lower the volume by 6dB, it might be good enough. To get 1 db steps, you'll need to multiply every sample by an attenuation factor from a db table. -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en To unsubscribe from this group, send email to android-developers+unsubscribegooglegroups.com or reply to this email with the words REMOVE ME as the subject.
[android-developers] Re: Modifying audio in real time
Hello Simone. What problems have you been facing with AudioTrack? Besides the fact that you will need to handle all the overhead of time/ streams controling everything should work fine with AudioTrack, even using the Emulator. For the volume change for example, try to each position of your audio streams for a float between 0.0f (no sound) and 1.0f (volume at 100%) and cast back to short before playing. Should give you the results you want. For the SampleRate, once AudioTrack is created you cannot change it´s samplerate value, but you can upsample/downsample your streams to get the desired efect. Hope it helps, Gabriel On 23 mar, 17:57, Simone simone.russ...@gmail.com wrote: Hi everyone, I'll try to explain briefly what I need to do. I need to load an audio resource and play it, but I also need to be able to modify some parameters (like the volume, or the playback rate) while the audio is being played. For example, I might want to play a 10 seconds audio stream, and change the volume only after 3 seconds. Is there a way to do it? I've been experimenting a little with AudioTrack without results. Thanks, Simone -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en To unsubscribe from this group, send email to android-developers+unsubscribegooglegroups.com or reply to this email with the words REMOVE ME as the subject.
