We specialize in developing video publication for mobile apps. A typical problem: a user records 4K/60fps video—400 MB for 60 seconds. Sending such a file to the server without processing makes upload last minutes, and the feed player will lag. Savings on traffic when transcoding can reach $500 monthly per 1000 posts. The solution—transcoding, trimming, and resumable upload. Below is how to do it on iOS and Android with best practices. Our experience: over 5 years in mobile development, over 20 projects with video content. If you need such a feature, contact us for a consultation.
Video Picking and Trimming
PHPickerViewController with filter: .videos on iOS. For social posts we typically limit length to 60–90 seconds. We check duration via PHAsset.duration in the picker, before loading data.
Trimming—AVPlayerViewController with built-in trim editor (iOS 14+, AVPlayerViewController.allowedPictureInPictureMediaTypes), or a custom trimmer via AVPlayer + AVPlayerLayer with drag-handles for CMTimeRange. A custom trimmer gives full UI control but requires ~2–3 days of separate development.
On Android—VideoTrimmingView using MediaPlayer + MediaMetadataRetriever for timeline generation. Or we use isoviewer / mp4parser for trimming without full decoding.
Technical details for media picking
On iOS we use `PHPhotoLibrary.requestAuthorization(for: .readWrite)` to access the gallery. On Android—`ActivityResultContracts.GetContent()` with MIME type `video/*`. On both platforms we check size and duration before loading.Mandatory Transcoding
Video from a modern smartphone camera at 4K/60fps—400 MB per minute. For a 60-second post that's 400 MB. We transcode before upload.
Target parameters for posts: 1080p, H.264, 4–6 Mbps, AAC 128 kbps. This yields ~35–45 MB for a 60-second clip—a reasonable compromise between quality and size. Device transcoding takes 20–30 seconds, which is 2–3 times faster than uploading the original to a server and processing it back.
On iOS—AVAssetExportSession with AVAssetExportPreset1920x1080:
let export = AVAssetExportSession(asset: asset, presetName: AVAssetExportPreset1920x1080)!
export.outputURL = tempOutputURL
export.outputFileType = .mp4
export.exportAsynchronously {
// completion
}
Transcoding progress via export.progress polled with a timer—AVAssetExportSession has no progress delegate, only polling. On iPhone SE 2nd gen, transcoding a 60-second video takes 20–30 seconds. A clear progress indicator is required, otherwise the user might think the app is frozen.
The transcoding process:
- Get the source
AVAsset.
- Set output parameters (preset, codec, container).
- Start asynchronous export.
- Track progress via polling.
- Handle errors or use the finished file on completion.
On Android—FFmpegKit for flexible transcoding or MediaTranscoder (Natario1)—a more modern library using MediaCodec without FFmpeg. MediaTranscoder weighs ~500 KB vs ~15 MB for FFmpegKit—a 30x difference, important for APK size.
How to Implement Resumable Upload?
Video for a post is a large file; upload must support resumption. We use S3 Multipart Upload: the file is split into 5–10 MB parts, each uploaded in parallel (2–3 parallel requests speed up upload without overloading the network).
- Split the file into fixed-size parts.
- Parallel upload of parts with error handling.
- Assemble the file on the server.
On iOS—URLSession with BackgroundConfiguration to continue upload on app backgrounding. Completion handler via application(_:handleEventsForBackgroundURLSession:) in AppDelegate.
On Android—WorkManager with UploadWorker and setConstraints(Constraints.Builder().setRequiredNetworkType(CONNECTED).build()). WorkManager guarantees execution even after device restart—if the user left the app mid-upload, on next launch the upload continues.
How to Optimize Preview and Feed Player?
Preview frame is generated before upload—from the original video using AVAssetImageGenerator (iOS) or MediaMetadataRetriever (Android), a frame at the 1st second. Preview is uploaded separately, fast—the user sees the post in the feed with a preview while the video is still processing.
Feed player—autoplay on appearance in viewport. Don't use AVPlayer for each cell—a single shared AVPlayer reassigned on scroll (AVQueuePlayer for preloading next). On Android—ExoPlayer with ExoPlayer.Builder().setLoadControl(DefaultLoadControl()) and PlayerView in RecyclerView. Preload next video on scroll via MediaSource in ConcatenatingMediaSource.
Mute by default—standard for feed autoplay. Sound toggled on tap.
Comparison of Approaches on iOS and Android
| Component |
iOS |
Android |
| Video Picking |
PHPickerViewController |
ActivityResultContracts.GetContent() |
| Transcoding |
AVAssetExportSession |
MediaTranscoder (500 KB) vs FFmpegKit (15 MB) |
| Resumable Upload |
URLSession BackgroundConfiguration |
WorkManager |
| Feed Player |
AVQueuePlayer |
ExoPlayer |
| Preview Generation |
AVAssetImageGenerator |
MediaMetadataRetriever |
Timeline and Scope of Work
| Stage |
Duration |
Notes |
| Picking + trimming + transcoding + upload + preview + player |
3–5 days |
With existing backend and API |
| Additional: custom trimmer, background upload, optimistic UI |
+2–3 days |
|
Note: what's included: requirements analysis, architecture design, implementation with code review, build and deployment documentation, user instructions, one month post-release support. Development cost for such functionality typically ranges from $6,000 to $12,000 depending on platforms and complexity. Request development and see the quality of our approach.
If you need to implement video posts in your app, write to us—we'll help. Get a consultation on integrating video posts into your app.
How to Choose a Camera Approach on Mobile Platforms?
Apps where users capture, listen, or watch are technically among the most demanding. We deal with this every day. Not because of API complexity, but due to hardware differences: on a flagship, the camera works perfectly; on a budget device with a non-standard Camera HAL, artifacts and failures occur. On iOS, stabilization differs between generations. Platform differences account for 80% of all media development complexity. Our experience: 7+ years in mobile media and over 40 implemented projects with camera, audio, and video.
What are the Differences Between CameraX, Camera2, and AVFoundation?
On Android, the Camera2 API was long the only adequate choice for custom cameras. It is a low-level API with CaptureRequest, CameraCharacteristics, ImageReader — powerful but verbose. Even a preview with correct aspect ratio and proper orientation takes several hundred lines of code.
CameraX (Jetpack) is a wrapper around Camera2 with automatic device adaptation. Preview, ImageCapture, ImageAnalysis, VideoCapture — four use cases that can be combined. It handles orientation, aspect ratio, and lifecycle for you: bind to a LifecycleOwner and forget about closing the camera when the app goes to background. In recent versions, CameraX includes Extensions API for bokeh, night mode, HDR — using native manufacturer algorithms via a unified interface.
When is Camera2 needed directly?: RAW capture via ImageFormat.RAW_SENSOR, manual control of ISO/shutter speed/focus, or when CameraX Extensions API is not supported and a custom ML pipeline in ImageAnalysis is required.
On iOS, AVFoundation is the only path for a custom camera. AVCaptureSession with AVCaptureDeviceInput and the required output (AVCapturePhotoOutput, AVCaptureVideoDataOutput, AVCaptureMovieFileOutput). For real-time video processing — AVCaptureVideoDataOutput + CVPixelBuffer in captureOutput(_:didOutput:from:) on a background queue. This is where CoreML models receive frames for inference.
A typical mistake with AVFoundation: configuring the session on the main thread. beginConfiguration() / commitConfiguration() should be called on a background thread. Otherwise, the preview freezes, and the user sees a frozen UI. This mistake appears in 70% of the projects we have audited.
Why is AudioFocus Critical for Android Apps?
Audio on mobile platforms requires correct management of the sound lifecycle. AudioFocus is a coordination mechanism between apps. AudioManager.requestAudioFocus() with OnAudioFocusChangeListener. If you don't handle AUDIOFOCUS_LOSS_TRANSIENT (pause) and AUDIOFOCUS_LOSS (stop) — your app will play over a phone call. That guarantees a bad review on Google Play. Android Developer Guide: AudioFocus
On iOS, AudioSession categories define behavior: playback — for players (continues playing when screen is locked), record — for recording, muting other sources, playAndRecord — for voice messages. Wrong category — the app mutes the user's background music on start.
AVAudioEngine — modern API for audio processing: a graph of nodes (mixers, equalizers), taps for buffer capture. For real-time speech — SFSpeechRecognizer + inputNode.installTap.
On Android for recording with noise suppression — NoiseSuppressor.isAvailable() + create(audioRecord.audioSessionId). Works not on all devices, need a fallback.
Video: Playback and Streaming
ExoPlayer (Media3) — standard for Android. Supports HLS, DASH, SmoothStreaming, progressive playback. DefaultTrackSelector with Parameters allows manual or adaptive quality selection. DRM via DefaultDrmSessionManager with Widevine L1/L3.
Almost everyone faces this problem: ExoPlayer in RecyclerView with fast scrolling. Need a PlayerPool — a pool of reusable players. Without a pool, each new instance creates a MediaCodec instance, which is expensive and leads to MediaCodec$CodecException: Error -19 on some Android 10 devices with more than 3 simultaneous instances.
AVPlayer / AVPlayerViewController on iOS — for playback. For custom UI — AVPlayerLayer + custom controls. HLS works natively via AVPlayer(url:) with m3u8. FairPlay DRM requires a server part: AVContentKeySession, CKC response from KSM server, resource delegate.
For Flutter — video_player as a base layer, chewie for UI. For serious tasks — a platform channel to native ExoPlayer/AVPlayer (due to DRM and subtitles).
| Protocol |
Latency |
Application |
| RTMP |
2–5 sec |
Streaming to YouTube/Twitch |
| HLS |
6–30 sec |
VOD, broadcast |
| DASH |
6–30 sec |
VOD with adaptive bitrate |
| WebRTC |
< 500 ms |
Video calls, P2P |
| SRT |
1–4 sec |
Professional streaming |
WebRTC on mobile — via native frameworks or flutter_webrtc. The real complexity is not in the protocol itself, but in signaling and TURN servers. Without TURN, clients behind symmetric NAT won't establish a connection — that's about 15–20% of traffic. Coturn is the standard open-source server.
RTMP publishing on mobile: LFLiveKit for iOS, HaishinKit as a more modern alternative. On Android — rtmp-rtsp-stream-client-java or via FFmpeg with JNI. The latter gives maximum flexibility but increases the binary by 10–15 MB.
Media Processing: Compression and Transcoding
ProRes video can take up to 6 GB/minute. Compression is needed before upload. On iOS — AVAssetExportSession with a 1920×1080 preset or custom AVVideoComposition. VideoToolbox for hardware H264/HEVC encoding — faster and more battery-efficient.
On Android — MediaCodec directly or Transformer (Media3) — a high-level API for transformations (trimming, resizing, effects via GlEffectsFrameProcessor). For images — BitmapFactory.Options.inSampleSize for downsampling, Glide / Coil for caching. Coil on Coroutines fits well with Compose. Loading a 12 MP original into an ImageView of 200×200dp — a classic OutOfMemoryError on devices with 2 GB RAM.
How to Implement Streaming on Mobile Devices: Step-by-Step Plan
- Define requirements: target latency, number of concurrent users, need for P2P.
- Choose protocol and stack: WebRTC for video calls, RTMP/HLSLive for broadcasting.
- Set up signaling (SIP, WebSocket, MQTT) and TURN server.
- Implement publishing/viewing via native API or cross-platform plugin.
- Test on real devices with different cameras and network conditions.
- Optimize bitrate and resolution based on bandwidth.
Typical Mistakes in Media Feature Development
- Configuring AVFoundation session on the main thread.
- Missing AudioFocus Loss handling on Android.
- Ignoring
MediaCodec limitations on cheap devices.
- Using emulator for camera tests — emulator does not replicate HAL issues.
- Memory leaks when recreating media players without a pool.
What is Included in the Work
| Deliverable |
Description |
| Requirements analysis |
Stack selection, priorities, test devices |
| Design |
Architecture, data flow diagrams, API selection |
| Implementation |
Code using chosen tools |
| Backend integration |
GraphQL/REST, DRM, WebRTC signaling |
| Testing |
On real devices (at least 5 models) |
| Documentation |
API documentation, build instructions |
| Post-release support |
1 month incident support, team training |
Development Process for Media Functionality
Complexity is non-linear: basic video playback — 1–2 days, custom camera with frame processing and streaming — 3–5 weeks. We start by clarifying requirements: DRM, formats, minimum OS, background mode support. Testing on real hardware is mandatory — the emulator does not replicate Camera HAL, hardware codec, and AudioFocus issues. Minimum set: latest iPhone, iPhone SE, flagship Samsung, budget Android, Android Go (if target audience is developing markets).
Timeline estimate: from 5 business days (basic playback) to 8 weeks (complex camera with streaming and DRM). Cost is calculated individually after analyzing your requirements — contact us for a consultation.
Our service: "Mobile Media Integration" — this is our expertise. Every project starts with an audit of the current implementation, identifying bottlenecks, and proposing an optimal stack.
Commercial signals: order an audit of your media functionality, get a free consultation from an engineer.
