subhra74/xdm · error

Both period start and duration is missing

Error message

Both period start and duration is missing

What it means

When an MPD contains multiple <Period> elements, CalculatePeriodDurationsIfMissing computes each period's duration from its start/duration attributes. If a period defines neither start nor duration, the duration cannot be derived, so the method throws. This is an invariant check required to compute period boundaries for the segment list.

Solutions

  1. Add explicit start and/or duration attributes to every Period element in the manifest.
  2. If you control manifest generation, always emit mediaPresentationDuration plus per-period timing.
  3. Catch the error and reject the multi-period manifest, directing users to a single-period VOD rendition.
  4. Check whether the source manifest is actually valid with a DASH validator (e.g. DASH-IF conformance tool).

Example fix

// before
<Period id="p2"></Period>

// after
<Period id="p2" start="PT30S" duration="PT60S"></Period>
Defensive patterns

Strategy: validation

Validate before calling

var doc = new XmlDocument(); doc.LoadXml(mpdXml);
foreach (XmlNode p in doc.SelectNodes("//*[local-name()='Period']"))
    if (p.Attributes["start"] == null && p.Attributes["duration"] == null)
        throw new Exception("Period missing both start and duration");

Try / catch

try { return MpdParser.Parse(url, null); }
catch (Exception ex) when (ex.Message.Contains("Both period start and duration is missing"))
{ throw new InvalidManifestException("Multi-period MPD lacks timing attributes", ex); }

Prevention

When it happens

Trigger: Parsing a multi-period MPD (periods.Count > 1) in which at least one Period element lacks both a start attribute and a duration attribute, and the duration can't be inferred from the next period or mediaPresentationDuration.

Common situations: Hand-edited or programmatically generated multi-period manifests missing timing attributes; ad-inserted streams where dynamic periods are added without start times; manifests relying on features (e.g. Period@id continuity / implicit timing) this parser doesn't implement.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of subhra74/xdm@1ca5a25aae (2026-09-13). Data as JSON: /api/errors/e94ca58d390c8f63. Report an issue: GitHub.

Appendix: source

Thrown at app/XDM/XDM.Core/MediaParser/Dash/MpdParser.cs:378

        public static IList<long> CalculatePeriodDurationsIfMissing(XmlNodeList periods, long mediaPresentationDuration)
        {
            var stack = new Stack<XmlNode>();
            foreach (XmlNode node in periods)
            {
                stack.Push(node);
            }
            var list = new List<long>(periods.Count);
            var last = mediaPresentationDuration;
            var count = stack.Count;
            for (int i = 0; i < count; i++)
            {
                var node = stack.Pop();
                var sduration = node.Attributes["duration"]?.Value;
                var sstart = node.Attributes["start"]?.Value;
                if (sstart == null && sduration == null)
                {
                    throw new Exception("Both period start and duration is missing");
                }
                if (sduration != null)
                {
                    var duration = DashUtil.ParseXsDuration(sduration);
                    list.Add(duration);
                    last = mediaPresentationDuration - duration;
                    continue;
                }
                if (sstart == null && i == stack.Count - 1)
                {
                    sstart = "PT0S";
                }
                var start = DashUtil.ParseXsDuration(sstart);
                list.Add(last - start);
                last = start;
            }
            list.Reverse();
            return list;

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