conditioning ¶

@torch.no_grad()
def forward(
    self,
    batch: ForwardBatch,
    fastvideo_args: FastVideoArgs,
) -> ForwardBatch:
    """
    Apply conditioning to the diffusion process.

    Args:
        batch: The current batch information.
        fastvideo_args: The inference arguments.

    Returns:
        The batch with applied conditioning.
    """
    # Forward is a no-op: CFG is applied via two separate
    # transformer forward passes inside DenoisingStage (e.g.
    # denoising.py:364-394, :706, :930). The class is kept because
    # verify_input / verify_output still validate CFG fields and
    # disable CFG when prompt_embeds is empty.
    return batch

def verify_input(self, batch: ForwardBatch, fastvideo_args: FastVideoArgs) -> VerificationResult:
    """Verify conditioning stage inputs."""
    result = VerificationResult()
    if not batch.prompt_embeds:
        # No text encoder/prompt embeddings: skip checks and effectively disable CFG.
        batch.do_classifier_free_guidance = False
        return result
    result.add_check("do_classifier_free_guidance", batch.do_classifier_free_guidance, V.bool_value)
    result.add_check("guidance_scale", batch.guidance_scale, V.positive_float)
    # Matrix-Game allow empty prompt
    # embeddings when CFG isn't enabled.
    if batch.do_classifier_free_guidance or batch.prompt_embeds:
        result.add_check("prompt_embeds", batch.prompt_embeds, V.list_not_empty)
        result.add_check("negative_prompt_embeds", batch.negative_prompt_embeds,
                         lambda x: not batch.do_classifier_free_guidance or V.list_not_empty(x))
    return result

def verify_output(self, batch: ForwardBatch, fastvideo_args: FastVideoArgs) -> VerificationResult:
    """Verify conditioning stage outputs."""
    result = VerificationResult()
    if batch.prompt_embeds is None or not batch.prompt_embeds:
        batch.do_classifier_free_guidance = False
        return result
    if batch.do_classifier_free_guidance or batch.prompt_embeds:
        result.add_check("prompt_embeds", batch.prompt_embeds, V.list_not_empty)
    return result