I am developing an app for iOS devices that is supposed to have a waveforms of music files like on SoundCloud. The problem is that I have achieved generation of waveform of fully downloaded file, how to generate a waveform of streaming audio during its playback? If someone's aware of how SoundCloud presents its waveforms please reply.
If we are talking about SoundCloud, for displaying an audio waveform, what I think is that they are -somehow- working with metadata for each specific audio to draw its desired waveform; Why it might be right? that's because the waveform will be drawn for each audio even before playing it (without waiting for streaming it). Applying the previous approach might be suitable solution for your issue.
However, I suggest to checkout this library, it might contains what are you looking for (drawing the waveform while streaming the audio file).
Also checking this Q&A might be helpful to your case.
Hope this helped.
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I am building an app that streams video content, something like TikTok. So you can swipe videos in table, and when new cell becomes visible the video starts playing. And it works great, except when you compare it to TikTok or Instagram or ect. My video starts streaming pretty fast but not always, it is very sensible to network quality, and sometimes even when network is great it still buffering too long. When comparing to TikTok, Instagram ... in same conditions they don't seam to have that problem. I am using JWPlayer as video hosting service, and AVPlayer as player. I am also doing async preload of assets before assigning them to PlayerItem. So my question is what else can I do to speed up video start. Do I need to do some special video preparations before uploading it to streaming service. (also I stream m3U8 files). Is there some set of presets that enables optimum streaming quality and start speed. Thanks in advance.
So theres a few things you can do.
HLS is apples preferred method of streaming to an apple device. So try to get that as much as possible for iOS devices.
The best practices when it comes to mobile streaming is offering multiple resolutions. The trick is to start with the lowest resolution available to get the video started. Then switch to a higher resolution once the speed is determined to be capable of higher resolutions. Generally this can be done quickly that the user doesn't really notice. YouTube is the best example of this tactic. HLS automatically does this, not sure about m3U8.
Assuming you are offering a UICollectionView or UITableView, try to start low resolution streams of every video on the screen in the background every time the scrolling stops. Not only does this allow you to do some cool preview stuff based off the buffer but when they click on it the video is already established. If thats too slow try just the middle video.
Edit the video in the background before upload to only be at the max resolution you expected it to be played at. There is no 4k resolution screen resolutions on any iOS device and probably never will be so cut down the amount of data.
Without getting more specifics this is all I got for now. Hope I understood your question correctly. Good luck!
I m going to develop audio track editing app in ios.
I've created waveform of audio file already. And going to implement "copy" feature of selected waveform.
For this, I've get part data of NSData (audio file's) and draw waveform again with copied part data.
This formal way cant provide high speed to draw waveform for each actions (paste, delete).
So my questions is what is the best way to edit audio track ?
I will appreciate if anyone let me know similar open source link or blog link.
Thanks in advice
I'm looking for a way to create a audio bars visualizer similar to this in iOS.
Every white bar will move up and down depending of audio wave. I'm really lost because haven't much experience dealing with audio in Objective-c.
EDIT: What i'm seeking is what Overcast's app does on its visualizer (the group of vertical orange bars on the lower part of the podcast's image)
Anyone can help?
Thanks
EDIT: Thanks to Tomer's answer I finally made it. First I did this tutorial in order to make it all clear. Then I created my own VisualizerView for my project, you can find it in this gist. Maybe is not perfect but it does what I needed to do.
Generally, you have a few options if you want to get an idea of what something sounds like in iOS:
Use the simple AVAudioPlayer audio player, and then use the [audioPlayer averagePowerForChannel:] method to get the avarage audio level for the current moment. Check out this tutorial.
Use the Audio Queue API, which lets you send whatever audio you want to the speaker: You would read audio from your source and fill the buffers with it every time. (If you're reading from a file, use AVAssetReader) This way you always know exactly what waveform you're playing, so you can, for example, calculate its avarage power or process it in other ways like FFT. Then you'd update the bars accordingly.
EDIT: The standard way of doing such a thing is to use the Fast Fourier Transform (FFT) - it extracts frequency information from a sound. Here's a good example of using it on iOS (Apple's guide here). But, of course, to use it you have to know exactly what waveform you're playing every time, so you'd probably want to use a lower-level API such as Audio Queue.
I am recording videos and playing them back using AVFoundation. Everything is perfect except the hissing which is there in the whole video. You can hear this hissing in every video captured from any iPad. Even videos captured from Apple's inbuilt camera app has it.
To hear it clearly, you can record a video in a place as quiet as possible without speaking anything. It can be very easily detected through headphones and keeping volume to maximum.
After researching, I found out that this hissing is made by preamplifier of the device and cannot be avoided while recording.
Only possible solution is to remove it during post processing of audio. Low frequency noise can be removed by implementing low pass filter and noise gates. There are applications and software like Adobe Audition which can perform this operation. This video shows how it is achieved using Adobe Audition.
I have searched Apple docs and found nothing which can achieve this directly. So I want to know if there exists any library, api or open source project which can perform this operation. If not, then how can I start going in right direction because it does looks like a complex task.
I have just built VLC library for iOS at VLCKit
and using it to display a video stream. I need to make it displays in real-time with a lowest latency, so I tried to find a way to reduce the number of buffered frames (or something similar to it) before display on an UIView.
I started looking in the module MobileVLCKit but it seems no property allows me to control that.
I am wondering if the change can be accomplished on MobileVLCKit itself or on the VLC library.
If so, will I need to modify the library and rebuild it? What is the parameter should I need to change?
After spending a mount of time to look into the vlc library without successful, I tried to stream with rtsp instead of rtmp protocol and the real-time of video produced has been improved.
Thus i also found a workaround solution by setting a timer to force player moves forward the buffered frames. It might cause jagging but keep video in more real-time.