samsung-wasm-decoder

Drop-in (mostly) API-compatible implementation of nacl-decoder, but using Samsung's WASM EMSS (ElementaryMediaStreamSource) + a <video> element.

JS/TS API

This package exports the same symbols as nacl-decoder:

• createNaClDecoder() (creates a WASM-backed decoder)
• isNaClSupported() (checks WebAssembly + Samsung EMSS bindings)
• NaClDecoder (class)
• VideoDecoder, VideoProfile, HWAcceleration, ResultStatus

Rendering happens via a <video> element (default id: video-element).

Expected runtime

The TS wrapper expects an Emscripten module instance available as:

• globalThis.SamsungWasmDecoderModule

The native module must export the C functions declared in native/decoder.cpp.

Build (native / emscripten CLI)

This project is intended to be built with Samsung-customized Emscripten SDK (the one that provides Tizen WebAssembly extensions). The upstream emsdk typically will not have the samsung/* headers and EMSS runtime.

If you only need a local emcc toolchain on your dev machine, native/Makefile also includes an optional upstream emsdk bootstrap (downloaded into ./emscripten/). This is useful to get emcc into PATH, but it still won’t provide Samsung’s EMSS headers unless you use Samsung’s customized SDK.

Prerequisites

• Samsung customized Emscripten SDK installed and activated (so emcc is on PATH).
• A shell session where the SDK env is loaded (often via source /path/to/emsdk_env.sh).

Compile

cd /mnt/data/home/misak113/dev/supraio/samsung-wasm-decoder/native

# If your Samsung emsdk isn't already active:
source /path/to/samsung-emsdk/emsdk_env.sh

make clean
make

Bootstrap emcc locally (optional)

If you don’t have emcc available, you can bootstrap an upstream emsdk into this repo:

cd /mnt/data/home/misak113/dev/supraio/samsung-wasm-decoder/native

make emsdk
make all-emsdk

This downloads emsdk into samsung-wasm-decoder/emscripten/emsdk and builds in a subshell that sources emsdk_env.sh.

Outputs:

• native/dist/samsung_wasm_decoder.js
• native/dist/samsung_wasm_decoder.wasm

Build flags (why they matter)

The native/Makefile uses the same required flags described in Samsung’s WebAssemblyDemos EMSS samples:

• -s ENVIRONMENT_MAY_BE_TIZEN (enables Samsung Tizen Emscripten extensions; required for EMSS)
• -pthread -s USE_PTHREADS=1 -s PTHREAD_POOL_SIZE=1 (EMSS samples use threads; pool size must be >= threads you create)

If headers/libs aren’t found

If your SDK does not expose the Samsung extension headers on default include paths, pass extra include/link flags:

make EXTRA_CFLAGS='-I/path/to/samsung/extensions/include' \
		 EXTRA_LDFLAGS='-L/path/to/samsung/extensions/lib'

Runtime loading

The native build is modularized (-s MODULARIZE=1 -s EXPORT_NAME=SamsungWasmDecoderModule). That means native/dist/samsung_wasm_decoder.js defines a factory function.

You must instantiate it and assign the resulting module instance to globalThis.SamsungWasmDecoderModule before calling createNaClDecoder():

// Option A: include the generated JS via <script> and then:
globalThis.SamsungWasmDecoderModule = await SamsungWasmDecoderModule({});

// Option B: if you bundle/pack it, ensure the factory is reachable and do the same.

After that:

import { createNaClDecoder, VideoProfile, HWAcceleration } from 'samsung-wasm-decoder';

const decoder = createNaClDecoder({ videoElementId: 'video-element' });
await decoder.initialize({
	graphics3DContext: { width: 1920, height: 1080 },
	profile: VideoProfile.H264High,
	acceleration: HWAcceleration.WithFallback,
	minPictureCount: 4,
});

// Feed Annex-B H264 access units:
await decoder.decode({ decodeId: 0, data: someNalAccessUnitArrayBuffer });

Notes

• Input to decode() / decodeAndRender() is expected to be H264 NAL access-unit bytes (commonly Annex-B). Keyframe detection is best-effort (IDR NAL type 5).
• getPicture() / render() / recyclePicture() are compatibility shims; for display use decoder.videoElement.