In this guide
Use a dependency example rather than a filename ruleTimestamps describe different scheduling questionsInspect before diagnosing a timing faultVideo prediction can require a picture to be decoded before another picture that appears earlier on screen. Frame reordering separates decode order from presentation order. Apple’s VideoToolbox documentation explicitly describes this relationship when B frames are encoded.
Reordering is an encoded-media timing property. It is not automatically evidence of network packets arriving in the wrong order or of visible motion judder.
Use a dependency example rather than a filename rule
An original simplified display sequence is A, B, C. If B uses information from A and C, the decoder needs C available before constructing B. A possible coded/decode sequence is therefore A, C, B, while the intended display sequence remains A, B, C.
Real codec structures can be more complex, and not every predicted-picture configuration uses this pattern. The example illustrates the dependency without claiming to be a playable bitstream.
Timestamps describe different scheduling questions
A presentation timestamp places a picture on the presentation timeline. A decoding timestamp, where provided by the format/tool, concerns decoding order or schedule. Values need their time base and stream context. A packet list ordered by decoding can therefore show presentation timestamps that are not numerically increasing.
Sorting encoded packets by presentation time is not a general repair: it can place a dependent picture before the reference it needs.
| Order or clock | Question |
|---|---|
| Decode order | When must pictures be processed to satisfy dependencies? |
| Presentation order | When should pictures appear? |
| Packet arrival time | When did network/application data arrive? |
| Wall-clock observation | When did the user observe an event? |
| Buffer/reorder delay | What timing cushion does the actual path require? |
Inspect before diagnosing a timing fault
Tools such as FFprobe can expose packet and stream information for media you are permitted to inspect. Preserve time-base units and both timestamp roles where available. A missing timestamp, an actual discontinuity or invalid media still needs investigation; the existence of reordering is not a blanket excuse for every anomaly.
For latency or stutter, correlate the encoded schedule with actual delivery and presentation evidence. Do not infer a fixed reordering delay from the codec family alone.