Node library to create an HLS by truncating the length of an HLS VOD.
npm install --save @eyevinn/hls-truncate
The code below shows an example on how an HLS VOD of 30 seconds can be truncated into a new VOD of approx 4 seconds.
const hlsVod = new HLSTruncateVod('http://testcontent.eyevinn.technology/slates/30seconds/playlist.m3u8', 4);
hlsVod.load()
.then(() => {
const mediaManifest = hlsVod.getMediaManifest(4928000);
console.log(mediaManifest);
});
What this library does can be illustrated by this simplified example below.
Consider the following:
#EXTM3U
#EXT-X-TARGETDURATION:3
#EXT-X-ALLOW-CACHE:YES
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-VERSION:3
#EXT-X-INDEPENDENT-SEGMENTS
#EXT-X-MEDIA-SEQUENCE:1
#EXTINF:3.000,
segment1_0_av.ts
#EXTINF:3.000,
segment2_0_av.ts
#EXTINF:3.000,
segment3_0_av.ts
#EXTINF:3.000,
segment4_0_av.ts
#EXTINF:3.000,
segment5_0_av.ts
#EXTINF:3.000,
segment6_0_av.ts
#EXTINF:3.000,
segment7_0_av.ts
#EXTINF:3.000,
segment8_0_av.ts
#EXTINF:3.000,
segment9_0_av.ts
#EXTINF:3.000,
segment10_0_av.ts
#EXT-X-ENDLIST
and with this library we can generate a new VOD by truncating to the nearest possible length (depending on segment length). Eg. for a target length of 5, this will result in:
#EXTM3U
#EXT-X-TARGETDURATION:3
#EXT-X-ALLOW-CACHE:YES
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-VERSION:3
#EXT-X-INDEPENDENT-SEGMENTS
#EXT-X-MEDIA-SEQUENCE:1
#EXTINF:3.000,
segment1_0_av.ts
#EXTINF:3.000,
segment2_0_av.ts
#EXT-X-ENDLIST
You can also provide a start-time offset.
const hlsVod = new HLSTruncateVod('http://testcontent.eyevinn.technology/slates/30seconds/playlist.m3u8', 4, { offset: 10 });
hlsVod.load()
.then(() => {
const mediaManifest = hlsVod.getMediaManifest(4928000);
console.log(mediaManifest);
});
The library will first remove 10 seconds (approx depending on segment length) and then take the next 4 seconds of the original playlist. For example consider this playlist:
#EXTM3U
#EXT-X-TARGETDURATION:3
#EXT-X-ALLOW-CACHE:YES
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-VERSION:3
#EXT-X-INDEPENDENT-SEGMENTS
#EXT-X-MEDIA-SEQUENCE:1
#EXTINF:3.000,
segment1_0_av.ts
#EXTINF:3.000,
segment2_0_av.ts
#EXTINF:3.000,
segment3_0_av.ts
#EXTINF:3.000,
segment4_0_av.ts
#EXTINF:3.000,
segment5_0_av.ts
#EXTINF:3.000,
segment6_0_av.ts
#EXTINF:3.000,
segment7_0_av.ts
#EXTINF:3.000,
segment8_0_av.ts
#EXTINF:3.000,
segment9_0_av.ts
#EXTINF:3.000,
segment10_0_av.ts
#EXT-X-ENDLIST
will result in:
#EXTM3U
#EXT-X-TARGETDURATION:3
#EXT-X-ALLOW-CACHE:YES
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-VERSION:3
#EXT-X-INDEPENDENT-SEGMENTS
#EXT-X-MEDIA-SEQUENCE:1
#EXTINF:3.000,
segment5_0_av.ts
#EXTINF:3.000,
segment6_0_av.ts
#EXT-X-ENDLIST
It will remove 12 seconds from the start (3 segments is 9 seconds and 4 segments is 12 seconds) and then truncate the remaining part to get a duration of 6 seconds (2 segments i 6 segments which is close to 4 seconds as requested).
This open source project is maintained by Eyevinn Technology.
- Jonas Birmé (jonas.birme@eyevinn.se)
- Alan Allard (alan.allard@eyevinn.se)
In addition to contributing code, you can help to triage issues. This can include reproducing bug reports, or asking for vital information such as version numbers or reproduction instructions.
Copyright 2021 Eyevinn Technology AB
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