CameraX Video UseCase Audio Quality

Although video recording is not yet officially supported in the CameraX library, you still can use the VideoCapture UseCase. There are plenty of StackOverflow and GitHub sample projects showing how to implement this, so I will not go over that here. What I will mention, however, is that none of the samples that I have seen so far address the audio quality.

When you are setting up your VideoCapture instance, you may have noticed VideoCaptureConfig has a couple audio methods. You may have also noticed that the default values for these will leave you with terrible audio quality, and that searching the web reveals nothing as to what you should use for these – no documentation from Google as it isn’t supported yet, and no samples I have seen so far touch on it. The relevant ones you should adjust will set the bit rate, sample rate, and audio channel count. Here’s an example:

    VideoCaptureConfig.Builder().apply {
        setAudioBitRate(320_000)
        setAudioSampleRate(44_100)
        setAudioChannelCount(2)

        /* setup other things here  */
    }

This will set a bitrate of 320bps, a sample rate of 44.1 kHz, and record in stereo. Your videos will sound much better!

Room Embedding @Embedded

Something I just discovered is that @Embedded‚Äč fields in Room entities can themselves contain @Embedded fields. For example:

data class Post(
    @Embedded
    val media: Media
)

data class Media(
    @Embedded
    val metadata: Metadata
)

data class Metadata(
    val resolution: String
)

works as you would expect, with resolution being pulled up to the Post entity table. Not sure how deeply @Embedded you can go, or if there are any performance consequences to this, but a neat trick!

Kotlin Android Extensions with ViewHolders

Something I recently discovered is how easy it is to use Kotlin’s Android View extensions with RecyclerView ViewHolders. Previously using Butterknife, many of my ViewHolder classes were simply a bunch of @BindViews with an init { ButterKnife.bind } . With Kotlin Android extensions, the views are declared as extensions on the ViewHolder’s ItemView field. Additionally, instead of declaring a ViewHolder class with one line, you can actually just use an anonymous object in your onCreateViewHolder method.

You could potentially use any of Kotlin’s scoping extension functions, I prefer to use let, so here’s what that looks like (note also the this[...] notation) :

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
        object : RecyclerView.ViewHolder(
            context.inflate(R.layout.adapter_thread, parent)
        ) {}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    val item = this[position]
    holder.itemView.let {
        it.viewIdTitle = item.title
        it.viewIdDescription = item.description
    }
}