Judging picture on the phone

The phone is a real handheld screen showing your real edit, which makes it useful for a set of judgements a desktop monitor cannot answer: how a grade reads at phone brightness, whether a shadow detail survives on a small screen, whether text is legible at the size your audience will see it. It is not a calibrated reference display, and this page is as specific as possible about where the line falls.

What this is and is not

It is: an 8-bit BT.709-class SDR picture, encoded at high quality, on the actual class of screen your audience uses.

It is not: color-managed, calibrated, HDR-capable, or 10-bit — at any setting, on either platform.

If your decision depends on absolute color accuracy, a hardware-calibrated reference display is what that decision needs. If it depends on how the image reads on a phone, this is the tool.

Recommended settings

Resolution Limit is on the HUD chip because it is the setting most likely to be wrong; the label on the chip is the current value.

The encoder runs in constant-quality mode, not constant bitrate. Quality is fixed at 75 out of 100, which on macOS maps to a per-frame base QP of 13 and on Windows sets the Media Foundation quality property to 75. There is no bitrate target you can tune, and on a LAN there is no practical bitrate ceiling — the nominal cap is 150 Mbps.

What happens to your pixels

Premiere Pro hands the plugin an 8-bit BGRA buffer at the sequence's frame size. Anything else is dropped rather than converted. From there:

The RGB-to-YUV step is where the two platforms genuinely diverge:

• Windows converts with an explicit BT.709 limited-range matrix in the plugin's own code, with 2×2 box averaging for chroma and no chroma siting offsets. The GPU compute-shader path is bit-identical to the CPU path.
• macOS hands VideoToolbox a BGRA pixel buffer and lets VideoToolbox do the conversion. No color properties are set on the compression session, so the matrix is whatever VideoToolbox picks by default.

Downscaling is not equal on the two platforms

This is the difference most likely to change a judgement you make.

Whenever Resolution Limit is below the source, the plugin receives a full-size frame from Premiere Pro and scales it before encoding. The scaler is not the same:

The Windows function is named BgraBoxDownscale and its comment claims a box filter. It is not one: it point-samples. Nothing is averaged.

At Source neither platform scales at all — the downscale is skipped entirely when the limit is zero, or at or above the source short side — so the two platforms are comparable there, and the picture is your picture.

macOS users can use a lower Resolution Limit for detail work with far less risk, because the resampling is correct. It is still a resample, so it still costs detail; it just does not alias.

Transparency composites to black

Premiere Pro's Transmit buffers carry straight alpha, and all three of the plugin's converters — the Windows CPU path, the Windows GPU shader and the macOS path — matte over black before encoding. The matte happens before any filtering that combines pixels, because averaging straight RGB and matting afterward computes the wrong value and leaves a halo along soft edges at every Resolution Limit below Source.

So a sequence with an empty background, an unrendered area, or a soft-edged effect such as a drop shadow shows on the phone composited onto black — matching what Premiere Pro's own Program Monitor displays. That is correct behavior, not a bug, and it means the phone is not the place to check what a title will look like over an unknown background.

HDR and Rec.2020 are not handled

There is no 10-bit path, no P010, no HEVC Main 10 profile, and no HDR transfer function anywhere in the encoder. The macOS profile is HEVC Main or H.264 High; Windows encodes NV12, which is 8-bit by definition.

An HDR or Rec.2020 sequence will stream — but it will be flattened into an 8-bit untagged picture with no tone mapping applied by the plugin. Whatever you see is the result of an unmanaged conversion, and it should not be used to judge an HDR grade.

The phone's contribution

The panel is the last stage of the chain and it is not neutral. Before you make a judgement, on the iPhone:

• Turn True Tone off — it warms the display to match ambient light.
• Turn Night Shift off, and check no Focus schedule is enabling it.
• Turn auto-brightness off and fix the brightness where you want it.

None of this is something the app can control, and none of it makes the phone calibrated. It makes it consistent, which is what lets you compare two versions of a grade on the same device and trust the difference.

Zoom

Pinch to zoom, double-tap to jump to 2.5×, double-tap again to return. The ceiling is a setting under gear → Max zoom, in stops from 2× to 30×.

Zoom is a client-side display scale on the decoded frame. Zooming does not request more detail from the host — at a downscaled Resolution Limit you are magnifying an already-scaled picture, and on Windows that means magnifying the aliasing. Raise Resolution Limit first, then zoom.

Traps worth knowing

4K HEVC on Windows can produce a silent black screen

If you are on Windows with an NVIDIA or Intel GPU, running HEVC, and you set Resolution Limit to Source or 2160p on a 4K sequence, you can end up with a connected, paired phone showing black — with no error on either side.

The chain: the setup window's Use NVIDIA / Intel HW HEVC encoder toggle defaults to off; with it off every asynchronous Media Foundation transform is skipped; NVIDIA and Intel expose hardware HEVC only as an asynchronous transform, so hardware HEVC becomes unavailable; the encoder falls through to the Media Foundation software HEVC transform; and software HEVC above 6 megapixels is refused outright — deliberately, because at 4K it blocked Premiere Pro's video thread past the host watchdog and Premiere Pro was killed with no crash dump.

The toggle is off by default; a Pro user choosing maximum quality is exactly who trips over it.

Fixes, in order of preference:

1. Turn Use NVIDIA / Intel HW HEVC encoder on in the plugin's setup window.
2. Switch Codec to H.264, which has no such cap — the software H.264 transform is CPU-bound at 4K but well-behaved.
3. Drop Resolution Limit to 1440p or below, which keeps the encoded frame under 6 megapixels.

The default 720p never trips this, and the free tier's 360p cap cannot reach it. It is specific to a Pro user asking for maximum quality on Windows.

Emergency compression

If a single encoded frame is large enough to overrun the wire's fragment ceiling, the plugin forces quality down to QP 51 — the worst available — for 30 frames, and requests a keyframe. This is a recovery path, not normal operation, but if you see a sudden burst of macroblocking on a very complex frame at Source resolution, that is what it was. It clears itself.

Note that on Windows' asynchronous hardware paths the QP override is not applied; only the forced keyframe is. So on NVIDIA and Intel hardware HEVC you may see the keyframe without the quality drop.

Related

• Picture and color — the full color path reference
• Encoding settings — every encoder control
• Limits — everything the product does not do
• Colors look wrong — diagnosing a mismatch
• No picture — including the black-screen case above