dateRanges[index].startDate undefined

[pmendozav]

Error:

Steps to replicate:

Unfortnately I cannot share the stream url but basically I was waiting for a long time and suddenly a playlist manifest started to include a tag EXT-X-DATERANGE with a field END-DATE but not START-DATE that m3u8-parser expects.

Basically I put a break point and wait:

here is the value for this:

Analysis

1. Observing this.lineStream.buffer:

#EXT-X-DATERANGE:ID="splice-0x9C6",END-DATE="2024-11-19T12:30:10.334833Z",DURATION=130.0,SCTE35-IN=0xFC302000000000000000FFF00F05000009C67F4FFF5A2E02770014000000008FBAEEA5
#EXTINF:6.16,
https://...52014694.ts
#EXTINF:6.0,
https://...52014695.ts

There is END-DATE but not START-DATE

2. To confirm, I checked t = this.manifest.dateRanges[e] with (e=1)

{
    "scte35In": "0xFC302000000000000000FFF00F05000009C67F4FFF5A2E02770014000000008FBAEEA5",
    "duration": 130,
    "endDate": "2024-11-19T12:30:10.334Z",
    "id": "splice-0x9C6"
}

3. My question:

In parser.js I see:

const dateRange = this.manifest.dateRanges[index]
// ...
if (dateRange.duration && dateRange.endDate) {
  const startDate = dateRange.startDate;
  const newDateInSeconds = startDate.getTime() + (dateRange.duration * 1000);

  this.manifest.dateRanges[index].endDate = new Date(newDateInSeconds);
}

So, are you checking if dateRange.endDate is defined to decide whether to update it? I'm unclear about that part. Shouldn't the criteria be dateRange.duration && dateRange.startDate? If dateRange.endDate is defined but one of the others is missing, we could just maintain the current daterange.endDate, right?

[adrums86]

I think the issue here is more so that the stream is providing invalid EXT-X-DATERANGE tags: Per the spec:

START-DATE

      A quoted-string containing the [[ISO_8601](https://datatracker.ietf.org/doc/html/draft-pantos-hls-rfc8216bis-16#ref-ISO_8601)] date/time at which the
      Date Range begins.  This attribute is REQUIRED.

Although the parser doesn't explicitly check in this case, I think the motivation behind the endDate check comes from this bit in the EXT-X-DATERANGE portion of the spec:

If a Date Range contains both a DURATION attribute and an END-DATE
   attribute, the value of the END-DATE attribute MUST be equal to the
   value of the START-DATE attribute plus the value of the DURATION
   attribute.

   Clients SHOULD ignore EXT-X-DATERANGE tags with illegal syntax.

All that said, I agree we should be avoiding this error by checking for startDate and never entering this block to begin with. I think we may want to check for startDate && endDate and do a quick equality check if we really want this to be spec compliant.

[pmendozav]

@adrums86 I added a warn event trigger if END-DATE and DURATION are present but START-DATE is missing. I also returned the END-DATE to the constraint to better align with the spec