samples/idol/README.md

# Long-form sample — an anime idol, 15 seconds

`idol-15s.mp4` is the one to watch: **14.7 s, 353 frames, 512x320, 24 fps**,
video and audio generated together, rendered on a **16 GB Tesla V100** from this
4-bit encoder. `prompt.txt` is the prompt, unedited.

It follows a lot of what was asked. Blonde hair, large blue eyes, star hair
ornament, the white and light-blue frilly dress with its navy ribbon, the bright
pastel bedroom with white furniture, blue curtains and a mirrored dresser. The
choreography lands in order too — it opens on a hand over the lens, peeking
through, then the presenting gesture, the shy eye-rub, the point at the camera.

## What it does not do

**It is not speaking Japanese, and probably not speaking at all.** The prompt
asked for it. There is audio — 14.7 s, 71% of its energy in the 300-3400 Hz band
a voice occupies — but its envelope peaks at **0.20 Hz**, and articulated speech
modulates at 3-8 Hz, once per syllable. The structure is closer to music or a
sustained vocalisation than to sentences. Judge it by ear; the measurement only
says do not expect dialogue.

**Style is not reliably controllable.** The same prompt, same encoder, same
seed, rendered at a different length or resolution, comes out photoreal instead
of animated:

| file | length | size | result |
|---|---|---|---|
| `idol-15s.mp4` | 14.7 s | 512x320 | **animated, on-prompt** |
| `idol-10s-4bit.mp4` | 9.7 s | 512x320 | photoreal, right scene |
| `idol-10s-768x512.mp4` | 9.7 s | 768x512 | photoreal, wrong scene — a dark stage with an audience |

Resolution and length change the latent shape, so they change the trajectory:
these are different samples, not the same sample rendered better or worse.

## That is the model, not the compression

`idol-10s-bf16.mp4` is the same prompt through the **BF16 original**, same DiT,
same seed, same size. It is photoreal too, and it tracks the 4-bit render
gesture for gesture at the same timestamps. So "2D anime animation" is being
ignored by LTX-2.5 itself at that length, and the encoder is not what dropped
it.

Frame-to-frame difference between the two, over all 233 frames: **MAE 0.0563**.
That is higher than the 0.0261 mean across the five benchmark prompts in
`../README.md` — a 317-token prompt with ten sequenced actions gives compression
more to lose than "a blacksmith hammers steel".

## Sharper: the pass these clips were missing

`idol-10s-1024x640-2pass.mp4` is the same prompt and seed as
`idol-10s-4bit.mp4`, run through the vendor's full pipeline instead of half of
it: sample at 512x320, upscale the latent 2x, sample again at 1024x640.

![one pass against two](https://huggingface.co/topabaem/LTX-2.5-Text-Encoder-4bit-8GB/resolve/main/samples/idol/sharpness-1pass-vs-2pass.png)

Left is the one-pass render enlarged afterwards, right is the two-pass render,
same frame, 1:1. Eyes, teeth, the star earring and the dress frills are separate
objects on the right and mush on the left — 4.1x the Laplacian variance on a
common grid.

**Every other clip here, and every clip in `../`, is one-pass.** The renderer
skipped that second pass on a written assumption that a 16 GB card could not
afford it. Measured, it peaks at 10.03 GiB and takes 312 s — it fits. So these
samples understate what the encoder drives, and the softness in them was never
the compression.

## Cost

| clip | wall clock | peak VRAM |
|---|---:|---:|
| 15 s, 512x320 | 123 s | 6.26 GiB |
| 10 s, 512x320 | 165 s | 6.10 GiB |
| 10 s, 768x512 | 178 s | 6.53 GiB |

All on one 16 GB V100 with `--fp16-unet --novram`. Fifteen seconds costs no more
memory than ten; the length ceiling here was not reached.