Technical Details

FastStream Archive Files (.fsa)

In some select cases, it is not feasible to convert the contents of a buffer into an MP4 on the browser (not without ffmpeg). Moreover, the buffer's required metadata varies depending on the media type. For this reason, we propose a new file format to store arbitrary information with ultrafast writing/parsing speeds for the browser environment.

Structure

Using example stream https://test-streams.mux.dev/x36xhzz/x36xhzz.m3u8. Numerical values use Big Endian representation.

• 00 00 01 00: 4 byte header size (256)
• FSA Header: JSON header encoded as utf8 (see below)

{
    "version": 1,
    "number_of_entries": 66,
    "source": {
        "url": "https://test-streams.mux.dev/x36xhzz/x36xhzz.m3u8",
        "identifier": "https://test-streams.mux.dev/x36xhzz/x36xhzz.m3u8",
        "mode": "accelerated_hls",
        "headers": {}
    },
    "currentLevel": "0:4",
    "currentAudioLevel": "1:-1"
}

This header is followed by the entries. Each entry has the following format:

• 00 00 01 C8: 4 byte entry header size (456)
• JSON entry header encoded as utf8 (See below). Only whitelisted response headers are included (eg: content-range).

{
    "url": "https://test-streams.mux.dev/x36xhzz/x36xhzz.m3u8",
    "responseType": "text",
    "stats": {
        "aborted": false,
        "timedout": false,
        "loaded": 752,
        "total": 752,
        "retry": 0,
        "chunkCount": 0,
        "bwEstimate": 0,
        "loading": {
            "start": 112.39999997615814,
            "first": 115.79999995231628,
            "end": 116
        },
        "parsing": {
            "start": 1083.2000000476837,
            "end": 0
        },
        "buffering": {
            "start": 0,
            "first": 0,
            "end": 0
        }
    },
    "responseURL": "https://test-streams.mux.dev/x36xhzz/x36xhzz.m3u8",
    "responseHeaders": {},
    "dataSize": 752
}

• Entry data: dataSize bytes containing the data (example below)

#EXTM3U
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=2149280,CODECS="mp4a.40.2,avc1.64001f",RESOLUTION=1280x720,NAME="720"
url_0/193039199_mp4_h264_aac_hd_7.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=246440,CODECS="mp4a.40.5,avc1.42000d",RESOLUTION=320x184,NAME="240"
url_2/193039199_mp4_h264_aac_ld_7.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=460560,CODECS="mp4a.40.5,avc1.420016",RESOLUTION=512x288,NAME="380"
url_4/193039199_mp4_h264_aac_7.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=836280,CODECS="mp4a.40.2,avc1.64001f",RESOLUTION=848x480,NAME="480"
url_6/193039199_mp4_h264_aac_hq_7.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=6221600,CODECS="mp4a.40.2,avc1.640028",RESOLUTION=1920x1080,NAME="1080"
url_8/193039199_mp4_h264_aac_fhd_7.m3u8

Audio Configuration

The audio profile configuration file has the following format:

{
  "type": "audioProfile",
  "version": 1,
  "profiles": [
    {
      "label": "Profile 1",
      "channels": [
        {
          "id": 0,
          "gain": 1,
          "muted": false,
          "solo": false,
          "equalizerNodes": [],
          "compressor": {
            "enabled": false,
            "attack": 0.003,
            "knee": 30,
            "ratio": 12,
            "release": 0.25,
            "threshold": -24,
            "gain": 1
          }
        },
        {
          "id": 1,
          "gain": 1,
          "muted": false,
          "solo": false,
          "equalizerNodes": [],
          "compressor": {
            "enabled": false,
            "attack": 0.003,
            "knee": 30,
            "ratio": 12,
            "release": 0.25,
            "threshold": -24,
            "gain": 1
          }
        },
        {
          "id": 2,
          "gain": 1,
          "muted": false,
          "solo": false,
          "equalizerNodes": [],
          "compressor": {
            "enabled": false,
            "attack": 0.003,
            "knee": 30,
            "ratio": 12,
            "release": 0.25,
            "threshold": -24,
            "gain": 1
          }
        },
        {
          "id": 3,
          "gain": 1,
          "muted": false,
          "solo": false,
          "equalizerNodes": [],
          "compressor": {
            "enabled": false,
            "attack": 0.003,
            "knee": 30,
            "ratio": 12,
            "release": 0.25,
            "threshold": -24,
            "gain": 1
          }
        },
        {
          "id": 4,
          "gain": 1,
          "muted": false,
          "solo": false,
          "equalizerNodes": [],
          "compressor": {
            "enabled": false,
            "attack": 0.003,
            "knee": 30,
            "ratio": 12,
            "release": 0.25,
            "threshold": -24,
            "gain": 1
          }
        },
        {
          "id": 5,
          "gain": 1,
          "muted": false,
          "solo": false,
          "equalizerNodes": [],
          "compressor": {
            "enabled": false,
            "attack": 0.003,
            "knee": 30,
            "ratio": 12,
            "release": 0.25,
            "threshold": -24,
            "gain": 1
          }
        }
      ],
      "master": {
        "id": "master",
        "gain": 1,
        "mono": false,
        "equalizerNodes": [
          {
            "type": "peaking",
            "frequency": 190.4054190990115,
            "gainDb": 4.307692307692307,
            "q": 1
          }
        ],
        "compressor": {
          "enabled": false,
          "attack": 0.003,
          "knee": 30,
          "ratio": 12,
          "release": 0.25,
          "threshold": -24,
          "gain": 1
        }
      },
      "crosstalk": {
        "enabled": false,
        "decaygain": -370,
        "colorgain": 5,
        "microdelay": 89,
        "lowbypass": 250,
        "highbypass": 5000,
        "speakerdistance": 25,
        "headdistance": 70
      }
    }
  ]
}