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feat: additional --preview-interval values #1915

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feat: additional --preview-interval values #1915

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f739158
use `sd_get_preview_interval()`
vmobilis Aug 23, 2026
036b575
Merge branch 'leejet:master' into master
vmobilis Aug 27, 2026
cb2d258
Options for `preview-interval`
vmobilis Aug 27, 2026
1c6b83e
Description of preview options
vmobilis Aug 27, 2026
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2 changes: 1 addition & 1 deletion examples/cli/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,7 @@ struct SDCliParams {
options.int_options = {
{"",
"--preview-interval",
"interval in denoising steps between consecutive updates of the image preview file (default is 1, meaning updating at every step)",
"interval in denoising steps between consecutive updates of the image preview file (default is 1, meaning updating at every step). Set to -N to preview only the Nth single step. Set to 0 to preview the last step of 1st pass (base resolution / high noise) sampling",
&preview_interval},
{"",
"--output-begin-idx",
Expand Down
36 changes: 24 additions & 12 deletions src/stable-diffusion.cpp
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Expand Up @@ -259,6 +259,8 @@ class StableDiffusionGGML {
bool is_using_v_parameterization = false;
bool is_using_edm_v_parameterization = false;

bool preview_last_step = false;

size_t control_net_params_mem_size = 0;

std::shared_ptr<ModelManager> model_manager;
Expand Down Expand Up @@ -2639,6 +2641,18 @@ class StableDiffusionGGML {
float c_out = scaling[1];
float c_in = scaling[2];

bool preview_needed = preview.callback != nullptr;
if (preview_needed) {
int preview_interval = sd_get_preview_interval();
if (preview_interval > 0) { // every Nth step
preview_needed = step % preview_interval == 0;
} else if (preview_interval < 0) { // only (-N)th step
preview_needed = step == -preview_interval;
} else { // last step of base resolution / high noise pass
preview_needed = preview_last_step && step == steps;
}
}

std::vector<float> base_timesteps_vec = prepare_sample_timesteps(sigma, shifted_timestep);
std::vector<float> timesteps_vec = base_timesteps_vec;
sd::Tensor<float> audio_timesteps_tensor;
Expand Down Expand Up @@ -2669,21 +2683,17 @@ class StableDiffusionGGML {
if (!denoise_mask.empty()) {
denoised = denoised * denoise_mask + init_latent * (1.0f - denoise_mask);
}
if (sd_should_preview_denoised() && preview.callback != nullptr) {
if (step % sd_get_preview_interval() == 0) {
preview_image(step, denoised, version, preview.mode, preview.callback, preview.data, false);
}
if (preview_needed && sd_should_preview_denoised()) {
preview_image(step, denoised, version, preview.mode, preview.callback, preview.data, false);
}
report_sample_progress(step, steps, &last_progress_us);
sd::guidance::GuiderOutput output;
output.pred = denoised;
return output;
}

if (sd_should_preview_noisy() && preview.callback != nullptr) {
if (step % sd_get_preview_interval() == 0) {
preview_image(step, noised_input, version, preview.mode, preview.callback, preview.data, true);
}
if (preview_needed && sd_should_preview_noisy()) {
preview_image(step, noised_input, version, preview.mode, preview.callback, preview.data, true);
}

sd::Tensor<float> cond_out;
Expand Down Expand Up @@ -2892,10 +2902,8 @@ class StableDiffusionGGML {
if (!denoise_mask.empty()) {
denoised = denoised * denoise_mask + init_latent * (1.0f - denoise_mask);
}
if (sd_should_preview_denoised() && preview.callback != nullptr) {
if (step % sd_get_preview_interval() == 0) {
preview_image(step, denoised, version, preview.mode, preview.callback, preview.data, false);
}
if (preview_needed && sd_should_preview_denoised()) {
preview_image(step, denoised, version, preview.mode, preview.callback, preview.data, false);
}
report_sample_progress(step, steps, &last_progress_us);
output.pred = denoised;
Expand Down Expand Up @@ -5666,6 +5674,7 @@ SD_API bool generate_image(sd_ctx_t* sd_ctx,
ImageGenerationEmbeds embeds = std::move(*embeds_opt);

std::vector<sd::Tensor<float>> final_latents;
sd_ctx->sd->preview_last_step = true;
int64_t denoise_start = ggml_time_ms();
for (int b = 0; b < request.batch_count; b++) {
sd_cancel_mode_t cancel = sd_ctx->sd->get_cancel_flag();
Expand Down Expand Up @@ -5726,6 +5735,7 @@ SD_API bool generate_image(sd_ctx_t* sd_ctx,
return false;
}
int64_t denoise_end = ggml_time_ms();
sd_ctx->sd->preview_last_step = false;
LOG_INFO("generating %zu latent images completed, taking %.2fs",
final_latents.size(),
(denoise_end - denoise_start) * 1.0f / 1000);
Expand Down Expand Up @@ -6938,6 +6948,7 @@ SD_API bool generate_video(sd_ctx_t* sd_ctx,
}
LOG_DEBUG("sample(high noise) %dx%dx%d", W, H, T);

sd_ctx->sd->preview_last_step = true;
int64_t sampling_start = ggml_time_ms();
std::vector<float> high_noise_sigmas(plan.sigmas.begin(), plan.sigmas.begin() + plan.high_noise_sample_steps + 1);
plan.sigmas = std::vector<float>(plan.sigmas.begin() + plan.high_noise_sample_steps, plan.sigmas.end());
Expand Down Expand Up @@ -6968,6 +6979,7 @@ SD_API bool generate_video(sd_ctx_t* sd_ctx,
request.cache_params,
latents.video_positions);
int64_t sampling_end = ggml_time_ms();
sd_ctx->sd->preview_last_step = false;
if (x_t_sampled.empty()) {
LOG_ERROR("sampling(high noise) failed after %.2fs", (sampling_end - sampling_start) * 1.0f / 1000);
return false;
Expand Down
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