SIMA Plugin JSON Truth Map (Historical)

Snapshot date: 2026-02-17

This document preserves the February 2026 JSON-field usage findings for model-pipeline SIMA stages. References to "current" behavior below describe that snapshot.

Historical contract: The plugin names and required JSON fields below are not the Platform 3.0.0 deployment contract. Generic BoxDecode now uses neatobjectdecode, configured from the typed manifest stage and runtime properties. The old simaaiboxdecode requirements below do not define its application-facing configuration. See the current SIMA static manifest context contract for the active configuration and matching-package requirements.

1. Freeze Scope and Plugin Matrix

1.1 In-scope (model pipeline)

• simaaiprocesscvu used as:
  • preproc stage (kernel=preproc)
  • quant/tess stage (kernel=quanttess)
  • post stage wrapper for detess/dequant (kernel=detessdequant in model sequence, backend element is still simaaiprocesscvu in src/nodes/sima/DetessDequant.cpp)
• simaaiprocessmla
• simaaiboxdecode (generic boxdecode)
• detess/dequant/tess payload stages in tmp/gst/*:
  • detessdequant
  • detessellate
  • quantize
  • slicedequant

1.2 Out-of-scope

Generic CVU app plugins and custom graph utilities are out of scope for this truth map, including but not limited to:

• overlay, genericrender, argmax, nms*, groupkeypoints, distancecalculation, cv_process, cvresize, fastbev*, PyGast-plugins/*, deprecated plugins, and custom app/test scaffolding.

1.3 Source trees covered

Static extraction covered both trees requested:

• tmp/gst_plugins_source/gst/*
• tmp/gst/*

Mirror check:

• Same in both trees: genericboxdecode, detessdequant, detessellate, quantize, slicedequant
• Diverged: processcvu, processmla

1.4 Plugin matrix

Plugin / Stage	Currently required JSON keys (current code paths)	Inferable keys	Runtime properties (should not be static JSON)	MLA-only keys
simaaiprocesscvu (preproc/quanttess/post wrapper)	infer-first: wiring comes from ConfigManager::getBuffers() when available; JSON input_buffers/output_memory_order is fallback-only.	input_width/input_height can come from caps/runtime for graph 200/202; wiring arrays can be synthesized from CM metadata	runtime dims are renegotiated per frame; framework build no longer rewrites per-stage JSON wiring fields	quant/tess and post paths consume MLA tensor shape fields indirectly (input_depth, slice_*)
simaaiprocessmla	simaai__params, model_path, batch_size; outputs[*] is preferred but no longer hard-required when output shape fields can infer segment sizes	output segment sizes can be inferred from output_*/slice_* + dtype	input_segment_name optional runtime wiring aid; model path can be pack-derived	outputs, data_type, output_*, slice_*, quant params
simaaiboxdecode	Practically required by backend config loader: buffers.output.size, memory.next_cpu, system.out_buf_queue; class count resolution currently depends on implementation version	num_classes inferable from input_depth/slice_depth + num_in_tensor + decode_type (new source logic)	buffers.input[*].name rewired from upstream; thresholds/topk often runtime knobs	input_*, slice_*, data_type, num_in_tensor
detessdequant (legacy standalone GST element)	simaai__params plus parser fields: orig_img_width, orig_img_height, frame_width, frame_height, num_in_tensor, next_cpu, no_of_outbuf, out_sz, input_*, slice_*, q_scale, q_zp	none in plugin; higher-level shape inference exists in StageConfig	upstream buffer naming/CPU routing are runtime in wrapper flows	input_*, slice_*, q_scale, q_zp, num_in_tensor
detessellate payload (tmp/gst/detessellate)	accepts de_tess.* or root/static-contract equivalents (input_*, slice_*/output_*); buffers.input[0].offset optional (defaults 0)	tensor count and dims can be synthesized from manifest stage static fields	input name/path should be runtime-wired, not static	shape/slice contract
quantize payload (tmp/gst/quantize)	quant_scale, zero_point (JSON fallback)	input element count inferred from incoming buffer size	now consumes q_scale/q_zp metadata from upstream first, then JSON fallback	n/a (generic quantization)
slicedequant payload (tmp/gst/slicedequant)	reads section (slice_dequant/simaai__params/root) for shape fallback; quant JSON is fallback-only	quant first from runtime metadata; dims can be synthesized from manifest static contract	runtime metadata (q_scale/q_zp) is preferred transport	MLA output shape/quant contract

1.5 Manifest context transport (current)

• Pipeline context type: sima.model.manifest.v1
• ABI-safe plugin access: manifest_accessor_v1 in include/gst/SimaPluginStaticManifestAbi.h
• Stage lookup keys:
  • element_name (default)
  • logical_stage_id (from stage-id or stage_id pipeline property when set)
• Legacy manifest_json string remains for transition fallback.
• Framework node/model fragment builders now emit stage-id=<element-name> for SIMA model-path plugins so logical lookup is deterministic even when additional name transforms are applied.

2. Required Key Truth Map

2.1 Static extraction method

Extracted from explicit access points:

• json["..."]
• contains("...")
• parser helpers (parser_get_int, parser_get_double_array, etc.)

Key evidence locations:

• tmp/gst/processcvu/gstsimaaiprocesscvu.cpp:1667
• tmp/gst/processmla/gstsimaaiprocessmla.cpp:579
• tmp/gst/genericboxdecode/payload.cpp:61
• tmp/gst/detessdequant/gstsimaaidetessdequant.cpp:276
• tmp/gst/detessellate/detessellate.cpp:361
• tmp/gst/quantize/payload.cpp:124
• tmp/gst/slicedequant/payload.cpp:57

Runtime wiring/inference evidence:

• src/nodes/sima/Preproc.cpp:245
• src/nodes/sima/DetessDequant.cpp:238
• src/nodes/sima/SimaBoxDecode.cpp:158
• src/pipeline/runtime/StageConfig.cpp:296
• src/pipeline/runtime/StageConfig.cpp:411

2.2 Dynamic failure-injection method used

For registered plugins (simaaiprocesscvu, simaaiprocessmla, simaaiboxdecode, detessdequant):

• baseline: gst-launch-1.0 ... num-buffers=0
• mutate one key at a time (remove field)
• record startup/runtime failure behavior and message
• note: dynamic results reflect the currently registered runtime plugins on this host

For non-registered payload stages (detessellate, quantize, slicedequant):

• no direct GST element available in this runtime (gst-inspect-1.0 reports missing)
• dynamic key-removal was therefore limited to static/source classification for this pass

2.3 Categorized map (frozen)

simaaiprocesscvu

• hard required:
  • either CM buffer inference success or JSON fallback with:
    • input_buffers
    • output_memory_order
    • each input memories[*].segment_name
    • each input memories[*].graph_input_name
• soft/defaultable:
  • graph_name
  • input_width, input_height (optional JSON dims)
• duplicate/derived:
  • input_buffers[*].name (runtime-wired)
  • sink_pad_tensor_index_map from manifest context is now preferred for deterministic multi-input mapping
  • preproc dims from caps/runtime
• debug-only:
  • debug style fields not required for execution

Dynamic evidence:

• if CM inference fails and JSON wiring is missing -> startup fails with bus error
• if CM inference succeeds -> input_buffers/output_memory_order can be omitted
• if context indicates a model-managed multi-input stage and sink_pad_tensor_index_map is missing or ambiguous -> startup fails with bus error

simaaiprocessmla

• hard required:
  • simaai__params
  • model_path
  • batch_size
  • outputs[*].name
  • outputs[*].size
  • batch_sz_model when batch_size != 1
• soft/defaultable:
  • input_segment_name
• duplicate/derived:
  • output dims/types can be inferred from model metadata in higher layers
• debug-only:
  • none critical

Dynamic evidence:

• remove model_path -> uncaught nlohmann::json type error (ec=134)
• batch_size=2 and remove batch_sz_model -> uncaught type error (ec=134)
• remove outputs -> startup can pass with num-buffers=0, but runtime (num-buffers=1) hits SIGSEGV spin path

simaaiboxdecode

• hard required (current runtime behavior):
  • buffers.output.size
  • memory.next_cpu
  • system.out_buf_queue
• soft/defaultable (depends on implementation version):
  • num_classes may be inferred/fallback in newer source, but current runtime may only warn
  • decode_type may degrade to type-mismatch warning in current runtime
• duplicate/derived:
  • buffers.input[*].name runtime-wired
  • num_classes derivable from tensor shape (input_depth/slice_depth) for known decode families
• debug-only:
  • system.debug, system.dump_data

Dynamic evidence:

• remove memory.next_cpu -> uncaught type error abort (ec=134)
• remove system.out_buf_queue -> uncaught type error abort (ec=134)
• remove num_classes -> non-fatal JSON type mismatch warning (ec=0)

detessdequant (legacy standalone GST plugin)

• hard required:
  • simaai__params object
  • parser keys: orig_img_width, orig_img_height, frame_width, frame_height, num_in_tensor, next_cpu, no_of_outbuf, out_sz, input_height, input_width, input_depth, slice_height, slice_width, slice_depth, q_scale, q_zp
• soft/defaultable:
  • none in current code
• duplicate/derived:
  • some frame/original size fields are metadata-level and should be derivable
• debug-only:
  • debug, dump_data, inpath, ibufname, n_request, etc.

Dynamic evidence:

• remove simaai__params -> SIGSEGV spin path (timeout)
• remove num_in_tensor -> SIGSEGV spin path (timeout)

detessellate payload

• hard required:
  • resolved input/slice tensor fields (from de_tess.* or root/static-contract synthesized keys)
• soft/defaultable:
  • buffers.input[0].offset (defaults to 0)
  • num_in_tensor (derived from vector sizes when omitted)
• duplicate/derived:
  • shape vectors are derivable from manifest stage static tensors
• debug-only:
  • none

quantize payload

• hard required:
  • quant_scale
  • zero_point
• soft/defaultable:
  • none in current code
• duplicate/derived:
  • tensor element count derived from input byte size
• debug-only:
  • none

slicedequant payload

• hard required:
  • quant params for dequantization (q_scale, q_zp) resolved from runtime metadata or fallback config
  • tensor slice dims (input_*, output_depth/slice_depth) resolved from section/root/static-contract synthesis
• soft/defaultable:
  • scalar vs vector encoding for quant and shape keys
• duplicate/derived:
  • quant is preferred from runtime metadata; JSON remains fallback-only
• debug-only:
  • n/a

3. Controlled Removal Gate (from this frozen map)

Any JSON field removal must include all of:

1. Update this truth map classification for the field.
2. Add/update a failure-injection test case:
   • startup failure must be explicit (bus error), never crash.
3. For inferable/derived fields:
   • implement inference first,
   • retain caps/plugin option fallback,
   • keep JSON as last fallback only where still required.
4. Keep MLA-only JSON minimal:
   • only unresolved MLA metadata (shape/size/quant params) remains.
5. Keep strict CI gate enabled:
   • unit_sima_plugin_manifest_strict_model_pipeline_test
   • unit_sima_plugin_manifest_strict_fallback_test
   • and the corresponding Vulcan CI test lane in .github/workflows/vulcan-ci.yml.

4. Current risks found

• Several missing-key paths still abort with uncaught nlohmann::json exceptions or SIGSEGV instead of bus errors.
• detessdequant legacy path is crash-prone for missing parser keys.
• slicedequant ignores JSON entirely and uses compiled constants.
• Runtime/source divergence can reappear whenever rebuilt .so files are not copied from tmp/gst/*/build to deps/gst-plugins.