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fix(engine): emit hvc1 for streaming H.265 GPU outputs

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@Monster-GM is already working on this.

Since Oct 4, 2026.

  • #5029 by @Monster-GM — open

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
78/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
typescript
Domain
audio-video-rtc, testing-qa

Research direction

Locate buildStreamingArgs() on current main and inspect the existing argument-construction tests. Verify how software, VideoToolbox, and supported GPU H.265 branches build their commands, then add coverage for H.265 and H.264 cases. Done means every H.265 path has exactly one hvc1 tag while H.264 and VP9 remain unchanged.

Written by the indexing model from the issue text.

Description

Summary

The streaming encoder adds the MP4 hvc1 sample-entry tag for software H.265, but GPU H.265 branches can omit it. Those outputs may use FFmpeg's default hev1 tag even though the encoded HEVC stream itself is valid.

This reduces compatibility with Apple playback software and other consumers that expect parameter sets through an hvc1 sample entry.

Root cause

In buildStreamingArgs(), the existing:

args.push("-tag:v", "hvc1");

is nested inside the software-encoder branch. The common codec === "h265" decision is outside that branch, so VideoToolbox and the other supported GPU H.265 encoders do not necessarily receive the same container tag.

Affected version

Observed in HyperFrames v0.8.114 (01c6f6004a00ecfa6e77ab4025b47a46a5e925fc). Please confirm against current main.

Expected behavior

Every MP4 streaming H.265 path should append -tag:v hvc1 exactly once, independently of whether the selected encoder is libx265, VideoToolbox, NVENC, VAAPI, QSV, or AMF. H.264 and VP9 paths must remain unchanged.

Proposed change

Move the H.265 sample-entry decision after software/GPU encoder selection but keep it inside the common H.265 branch:

if (codec === "h265") {
  args.push("-tag:v", "hvc1");
}
Validation

Add argument-construction tests covering:

  • software H.265;
  • HDR VideoToolbox H.265;
  • each supported GPU H.265 encoder;
  • software and GPU H.264 negative cases;
  • exactly one hvc1 tag per H.265 command.

The change is container metadata only and does not alter encoded picture data, bitrate, transfer characteristics, or HDR metadata.

Dominant language
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Avg merge
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Merged PRs (30d)
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