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feat: Use ll-hls query directives and support skipping segments #1079

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merged 30 commits into from
May 26, 2021

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brandonocasey
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@brandonocasey brandonocasey commented Feb 22, 2021

Description

Implements "query directives" when supported by the server so that we can get delta playlist updates to offset the cost of requesting a manifests so frequently.

@brandonocasey brandonocasey force-pushed the feat/llhls-2 branch 2 times, most recently from eeba482 to 1161c6f Compare March 3, 2021 20:30
@brandonocasey brandonocasey force-pushed the feat/llhls-2 branch 2 times, most recently from 3309677 to 37ae651 Compare March 12, 2021 18:50
Base automatically changed from feat/llhls-2 to main April 5, 2021 16:17
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codecov bot commented Apr 8, 2021

Codecov Report

Merging #1079 (c555607) into main (1c7a63b) will increase coverage by 0.09%.
The diff coverage is 91.81%.

❗ Current head c555607 differs from pull request most recent head e8cd59d. Consider uploading reports for the commit e8cd59d to get more accurate results
Impacted file tree graph

@@            Coverage Diff             @@
##             main    #1079      +/-   ##
==========================================
+ Coverage   86.20%   86.30%   +0.09%     
==========================================
  Files          39       39              
  Lines        9289     9362      +73     
  Branches     2127     2155      +28     
==========================================
+ Hits         8008     8080      +72     
- Misses       1281     1282       +1     
Impacted Files Coverage Δ
src/playlist-loader.js 93.05% <90.90%> (+1.42%) ⬆️
src/playlist.js 94.28% <91.66%> (-0.22%) ⬇️
src/manifest.js 97.97% <100.00%> (+0.13%) ⬆️
src/segment-loader.js 95.82% <100.00%> (+0.01%) ⬆️

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@@ -632,11 +715,9 @@ export default class PlaylistLoader extends EventTarget {

this.src = resolveManifestRedirect(this.handleManifestRedirects, this.src, req);

const manifest = parseManifest({
const manifest = this.parseManifest_({
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move parseManifest to this.parseManifest as we weren't previously passing all the options in both calls.

@@ -146,28 +177,36 @@ export const isPlaylistUnchanged = (a, b) => a === b ||
* master playlist with the updated media playlist merged in, or
* null if the merge produced no change.
*/
export const updateMaster = (master, media, unchangedCheck = isPlaylistUnchanged) => {
export const updateMaster = (master, newMedia, unchangedCheck = isPlaylistUnchanged) => {
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I continuously got confused by media and playlist here and realized that they are just terrible names. Most of the changes in this function, other than those noted, are for this rename.

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thought (non-blocking): yeah, I'm sure have a lot of places where the terminology is confusing. We probably want to write up some guidelines around naming, particularly around words like media, playlist, etc.

return null;
}

const mergedPlaylist = mergeOptions(playlist, media);
newMedia.segments = getAllSegments(newMedia);
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preserve preloadSegment from newMedia during the merge that will happen below.


// if the update could overlap existing segment information, merge the two segment lists
if (playlist.segments) {
if (oldMedia.segments) {
if (newMedia.skip) {
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if we have skipped segments, add them back in so that we can merge information from the old media segments into them.


let uri = resolveUrl(this.master.uri, media.uri);

if (this.experimentalLLHLS) {
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This is all new, basically use query directives and server side blocking if available.

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question: do we want to skip these two server-control checks if we have an end list tag? The spec says that the server MUST ignore these, so, we may as well not do the calculations in those cases, if we don't already.

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sure I will make this an && !endList


let currentMap;

for (let newIndex = 0; newIndex < newSegments.length; newIndex++) {
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This function was completely changed. Previously we used to create a new array from newSegments and then loop over old segments, merging in old timing information and properties.

Now create an empty array for the result. Loop over every new segment and merge the accompanying old segment if we have one. Otherwise we just push the new segment into the list.

result.push(updateSegment(oldSegment, newSegment));
} else {
// carry over map to new segment if it is missing
if (currentMap && !newSegment.map) {
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The big push for the refactor of this function was:

using HLS_skip=YES also skips init segment maps that have already been seen, so we need to make sure that the map that was in use for the last old segment is merged into new segments.

src/manifest.js Outdated Show resolved Hide resolved
src/playlist.js Outdated Show resolved Hide resolved
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@@ -146,28 +177,36 @@ export const isPlaylistUnchanged = (a, b) => a === b ||
* master playlist with the updated media playlist merged in, or
* null if the merge produced no change.
*/
export const updateMaster = (master, media, unchangedCheck = isPlaylistUnchanged) => {
export const updateMaster = (master, newMedia, unchangedCheck = isPlaylistUnchanged) => {
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thought (non-blocking): yeah, I'm sure have a lot of places where the terminology is confusing. We probably want to write up some guidelines around naming, particularly around words like media, playlist, etc.


let uri = resolveUrl(this.master.uri, media.uri);

if (this.experimentalLLHLS) {
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question: do we want to skip these two server-control checks if we have an end list tag? The spec says that the server MUST ignore these, so, we may as well not do the calculations in those cases, if we don't already.

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gkatsev commented May 24, 2021

Also, was trying out https://conventionalcomments.org/. LMK what you think.

gkatsev
gkatsev previously approved these changes May 25, 2021
const parts = getLastParts(manifest);

if (parts.length && !manifest.partTargetDuration) {
const partTargetDuration = parts.reduce((acc, p) => Math.max(acc, p.duration), 0);
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Since the spec says:

4.4.3.7.  EXT-X-PART-INF

   The EXT-X-PART-INF tag provides information about the Partial
   Segments in the Playlist.  It is REQUIRED if a Playlist contains one
   or more EXT-X-PART tags.

https://datatracker.ietf.org/doc/html/draft-pantos-hls-rfc8216bis-09#section-4.4.3.7

I think we may be better off throwing an error on the manifest if it's not available and parts are present.

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In an ideal world I think we would, but we already guess at target duration above this so I think it makes sense to guess at partTargetDuration as well. Might be ok to log an error here though?

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I think an error would be good in that case. Maybe we can reference the spec too.

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We do log onwarn below. Is that sufficient?

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I don't think a warning log is sufficient, as this goes against a requirement of the spec.

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src/playlist-loader.js Outdated Show resolved Hide resolved
src/playlist-loader.js Outdated Show resolved Hide resolved
src/playlist-loader.js Show resolved Hide resolved
test/playlist-loader.test.js Outdated Show resolved Hide resolved
test/playlist-loader.test.js Outdated Show resolved Hide resolved
test/playlist-loader.test.js Outdated Show resolved Hide resolved
test/playlist-loader.test.js Outdated Show resolved Hide resolved
test/playlist-loader.test.js Outdated Show resolved Hide resolved
Co-authored-by: Garrett Singer <[email protected]>
src/manifest.js Outdated Show resolved Hide resolved
src/playlist-loader.js Outdated Show resolved Hide resolved
Co-authored-by: Garrett Singer <[email protected]>
@brandonocasey brandonocasey merged commit 458be2c into main May 26, 2021
@brandonocasey brandonocasey deleted the feat/llhls-3 branch May 26, 2021 20:18
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3 participants