Automatic Speech Recognition Python* Sample¶

This sample demonstrates how to do a Synchronous Inference of acoustic model based on Kaldi* neural models and speech feature vectors.

The sample works with Kaldi ARK or Numpy* uncompressed NPZ files, so it does not cover an end-to-end speech recognition scenario (speech to text), requiring additional preprocessing (feature extraction) to get a feature vector from a speech signal, as well as postprocessing (decoding) to produce text from scores.

Automatic Speech Recognition Python sample application demonstrates how to use the following Python API in applications:

Feature	API	Description
Import/Export Model	[openvino.runtime.Core.import_model], openvino.runtime.CompiledModel.export_model	The GNA plugin supports loading and saving of the GNA-optimized model
Model Operations	[openvino.runtime.Model.add_outputs], openvino.runtime.set_batch , [openvino.runtime.CompiledModel.inputs], openvino.runtime.CompiledModel.outputs , [openvino.runtime.ConstOutput.any_name]	Managing of model: configure batch_size, input and output tensors
Synchronous Infer	openvino.runtime.CompiledModel.create_infer_request , [openvino.runtime.InferRequest.infer]	Do synchronous inference
InferRequest Operations	openvino.runtime.InferRequest.get_input_tensor , [openvino.runtime.InferRequest.model_outputs], openvino.runtime.InferRequest.model_inputs ,	Get info about model using infer request API
InferRequest Operations	[openvino.runtime.InferRequest.query_state], openvino.runtime.VariableState.reset	Gets and resets CompiledModel state control
Profiling	[openvino.runtime.InferRequest.profiling_info], [openvino.runtime.ProfilingInfo.real_time]	Get infer request profiling info

Basic OpenVINO™ Runtime API is covered by Hello Classification Python* Sample.

Options	Values
Validated Models	Acoustic model based on Kaldi* neural models (see Model Preparation section)
Model Format	OpenVINO™ toolkit Intermediate Representation (.xml + .bin)
Supported devices	See Execution Modes section below and List Supported Devices
Other language realization	C++

How It Works¶

At startup, the sample application reads command-line parameters, loads a specified model and input data to the OpenVINO™ Runtime plugin, performs synchronous inference on all speech utterances stored in the input file, logging each step in a standard output stream.

You can see the explicit description of each sample step at Integration Steps section of “Integrate OpenVINO™ Runtime with Your Application” guide.

GNA-specific details¶

Quantization¶

If the GNA device is selected (for example, using the -d GNA flag), the GNA OpenVINO™ Runtime plugin quantizes the model and input feature vector sequence to integer representation before performing inference.

Several neural model quantization modes:

static - The first utterance in the input file is scanned for dynamic range. The scale factor (floating point scalar multiplier) required to scale the maximum input value of the first utterance to 16384 (15 bits) is used for all subsequent inputs. The neural model is quantized to accommodate the scaled input dynamic range.
user-defined - The user may specify a scale factor via the -sf flag that will be used for static quantization.

The -qb flag provides a hint to the GNA plugin regarding the preferred target weight resolution for all layers.

For example, when -qb 8 is specified, the plugin will use 8-bit weights wherever possible in the model.

Note

It is not always possible to use 8-bit weights due to GNA hardware limitations. For example, convolutional layers always use 16-bit weights (GNA hardware version 1 and 2). This limitation will be removed in GNA hardware version 3 and higher.

Execution Modes¶

Several execution modes are supported via the -d flag:

CPU - All calculation are performed on CPU device using CPU Plugin.
GPU - All calculation are performed on GPU device using GPU Plugin.
MYRIAD - All calculation are performed on Intel® Neural Compute Stick 2 device using VPU MYRIAD Plugin.
GNA_AUTO - GNA hardware is used if available and the driver is installed. Otherwise, the GNA device is emulated in fast-but-not-bit-exact mode.
GNA_HW - GNA hardware is used if available and the driver is installed. Otherwise, an error will occur.
GNA_SW - Deprecated. The GNA device is emulated in fast-but-not-bit-exact mode.
GNA_SW_FP32 - Substitutes parameters and calculations from low precision to floating point (FP32).
GNA_SW_EXACT - GNA device is emulated in bit-exact mode.

Loading and Saving Models¶

The GNA plugin supports loading and saving of the GNA-optimized model (non-IR) via the -rg and -wg flags.

Thereby, it is possible to avoid the cost of full model quantization at run time.

The GNA plugin also supports export of firmware-compatible embedded model images for the Intel® Speech Enabling Developer Kit and Amazon Alexa* Premium Far-Field Voice Development Kit via the -we flag (save only).

In addition to performing inference directly from a GNA model file, these options make it possible to:

Convert from IR format to GNA format model file (-m, -wg)
Convert from IR format to embedded format model file (-m, -we)
Convert from GNA format to embedded format model file (-rg, -we)

Running¶

Run the application with the -h option to see the usage message:

python speech_sample.py -h

Usage message:

usage: speech_sample.py [-h] (-m MODEL | -rg IMPORT_GNA_MODEL) -i INPUT [-o OUTPUT] [-r REFERENCE] [-d DEVICE] [-bs [1-8]]
                        [-layout LAYOUT] [-qb [8, 16]] [-sf SCALE_FACTOR] [-wg EXPORT_GNA_MODEL]
                        [-we EXPORT_EMBEDDED_GNA_MODEL] [-we_gen [GNA1, GNA3]]
                        [--exec_target [GNA_TARGET_2_0, GNA_TARGET_3_0]] [-pc] [-a [CORE, ATOM]] [-iname INPUT_LAYERS]
                        [-oname OUTPUT_LAYERS] [-cw_l CONTEXT_WINDOW_LEFT] [-cw_r CONTEXT_WINDOW_RIGHT] [-pwl_me PWL_ME]

optional arguments:
  -m MODEL, --model MODEL
                        Path to an .xml file with a trained model (required if -rg is missing).
  -rg IMPORT_GNA_MODEL, --import_gna_model IMPORT_GNA_MODEL
                        Read GNA model from file using path/filename provided (required if -m is missing).

Options:
  -h, --help            Show this help message and exit.
  -i INPUT, --input INPUT
                        Required. Path to an input file (.ark or .npz).
  -o OUTPUT, --output OUTPUT
                        Optional. Output file name to save inference results (.ark or .npz).
  -r REFERENCE, --reference REFERENCE
                        Optional. Read reference score file and compare scores.
  -d DEVICE, --device DEVICE
                        Optional. Specify a target device to infer on. CPU, GPU, MYRIAD, GNA_AUTO, GNA_HW, GNA_SW_FP32,
                        GNA_SW_EXACT and HETERO with combination of GNA as the primary device and CPU as a secondary (e.g.
                        HETERO:GNA,CPU) are supported. The sample will look for a suitable plugin for device specified.
                        Default value is CPU.
  -bs [1-8], --batch_size [1-8]
                        Optional. Batch size 1-8.
  -layout LAYOUT        Optional. Custom layout in format: "input0[value0],input1[value1]" or "[value]" (applied to all
                        inputs)
  -qb [8, 16], --quantization_bits [8, 16]
                        Optional. Weight bits for quantization: 8 or 16 (default 16).
  -sf SCALE_FACTOR, --scale_factor SCALE_FACTOR
                        Optional. The user-specified input scale factor for quantization. If the model contains multiple
                        inputs, provide scale factors by separating them with commas.
  -wg EXPORT_GNA_MODEL, --export_gna_model EXPORT_GNA_MODEL
                        Optional. Write GNA model to file using path/filename provided.
  -we EXPORT_EMBEDDED_GNA_MODEL, --export_embedded_gna_model EXPORT_EMBEDDED_GNA_MODEL
                        Optional. Write GNA embedded model to file using path/filename provided.
  -we_gen [GNA1, GNA3], --embedded_gna_configuration [GNA1, GNA3]
                        Optional. GNA generation configuration string for embedded export. Can be GNA1 (default) or GNA3.
  --exec_target [GNA_TARGET_2_0, GNA_TARGET_3_0]
                        Optional. Specify GNA execution target generation. By default, generation corresponds to the GNA HW
                        available in the system or the latest fully supported generation by the software. See the GNA
                        Plugin's GNA_EXEC_TARGET config option description.
  -pc, --performance_counter
                        Optional. Enables performance report (specify -a to ensure arch accurate results).
  -a [CORE, ATOM], --arch [CORE, ATOM]
                        Optional. Specify architecture. CORE, ATOM with the combination of -pc.
  -iname INPUT_LAYERS, --input_layers INPUT_LAYERS
                        Optional. Layer names for input blobs. The names are separated with ",". Allows to change the order
                        of input layers for -i flag. Example: Input1,Input2
  -oname OUTPUT_LAYERS, --output_layers OUTPUT_LAYERS
                        Optional. Layer names for output blobs. The names are separated with ",". Allows to change the
                        order of output layers for -o flag. Example: Output1:port,Output2:port.
  -cw_l CONTEXT_WINDOW_LEFT, --context_window_left CONTEXT_WINDOW_LEFT
                        Optional. Number of frames for left context windows (default is 0). Works only with context window
                        models. If you use the cw_l or cw_r flag, then batch size argument is ignored.
  -cw_r CONTEXT_WINDOW_RIGHT, --context_window_right CONTEXT_WINDOW_RIGHT
                        Optional. Number of frames for right context windows (default is 0). Works only with context window
                        models. If you use the cw_l or cw_r flag, then batch size argument is ignored.
  -pwl_me PWL_ME        Optional. The maximum percent of error for PWL function. The value must be in <0, 100> range. The
                        default value is 1.0.

Model Preparation¶

You can use the following model optimizer command to convert a Kaldi nnet1 or nnet2 neural model to OpenVINO™ toolkit Intermediate Representation format:

mo --framework kaldi --input_model wsj_dnn5b.nnet --counts wsj_dnn5b.counts --remove_output_softmax --output_dir <OUTPUT_MODEL_DIR>

The following pre-trained models are available:

wsj_dnn5b_smbr
rm_lstm4f
rm_cnn4a_smbr

All of them can be downloaded from https://storage.openvinotoolkit.org/models_contrib/speech/2021.2.

Speech Inference¶

You can do inference on Intel® Processors with the GNA co-processor (or emulation library):

python speech_sample.py -m wsj_dnn5b.xml -i dev93_10.ark -r dev93_scores_10.ark -d GNA_AUTO -o result.npz

NOTES :

Before running the sample with a trained model, make sure the model is converted to the intermediate representation (IR) format (*.xml + *.bin) using the Model Optimizer tool.
The sample supports input and output in numpy file format (.npz)

Sample Output¶

The sample application logs each step in a standard output stream.

[ INFO ] Creating OpenVINO Runtime Core
[ INFO ] Reading the model: /models/wsj_dnn5b_smbr_fp32.xml
[ INFO ] Using scale factor(s) calculated from first utterance
[ INFO ] For input 0 using scale factor of 2175.4322418
[ INFO ] Loading the model to the plugin
[ INFO ] Starting inference in synchronous mode
[ INFO ]
[ INFO ] Utterance 0:
[ INFO ] Total time in Infer (HW and SW): 6326.06ms
[ INFO ] Frames in utterance: 1294
[ INFO ] Average Infer time per frame: 4.89ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.7051840
[ INFO ] avg error: 0.0448388
[ INFO ] avg rms error: 0.0582387
[ INFO ] stdev error: 0.0371650
[ INFO ]
[ INFO ] Utterance 1:
[ INFO ] Total time in Infer (HW and SW): 4526.57ms
[ INFO ] Frames in utterance: 1005
[ INFO ] Average Infer time per frame: 4.50ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.7575974
[ INFO ] avg error: 0.0452166
[ INFO ] avg rms error: 0.0586013
[ INFO ] stdev error: 0.0372769
[ INFO ]
[ INFO ] Utterance 2:
[ INFO ] Total time in Infer (HW and SW): 6636.56ms
[ INFO ] Frames in utterance: 1471
[ INFO ] Average Infer time per frame: 4.51ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.7191710
[ INFO ] avg error: 0.0472226
[ INFO ] avg rms error: 0.0612991
[ INFO ] stdev error: 0.0390846
[ INFO ]
[ INFO ] Utterance 3:
[ INFO ] Total time in Infer (HW and SW): 3927.01ms
[ INFO ] Frames in utterance: 845
[ INFO ] Average Infer time per frame: 4.65ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.7436461
[ INFO ] avg error: 0.0477581
[ INFO ] avg rms error: 0.0621334
[ INFO ] stdev error: 0.0397457
[ INFO ]
[ INFO ] Utterance 4:
[ INFO ] Total time in Infer (HW and SW): 3891.49ms
[ INFO ] Frames in utterance: 855
[ INFO ] Average Infer time per frame: 4.55ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.7071600
[ INFO ] avg error: 0.0449147
[ INFO ] avg rms error: 0.0585048
[ INFO ] stdev error: 0.0374897
[ INFO ]
[ INFO ] Utterance 5:
[ INFO ] Total time in Infer (HW and SW): 3378.61ms
[ INFO ] Frames in utterance: 699
[ INFO ] Average Infer time per frame: 4.83ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.8870468
[ INFO ] avg error: 0.0479243
[ INFO ] avg rms error: 0.0625490
[ INFO ] stdev error: 0.0401951
[ INFO ]
[ INFO ] Utterance 6:
[ INFO ] Total time in Infer (HW and SW): 4034.31ms
[ INFO ] Frames in utterance: 790
[ INFO ] Average Infer time per frame: 5.11ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.7648273
[ INFO ] avg error: 0.0482702
[ INFO ] avg rms error: 0.0629734
[ INFO ] stdev error: 0.0404429
[ INFO ]
[ INFO ] Utterance 7:
[ INFO ] Total time in Infer (HW and SW): 2854.04ms
[ INFO ] Frames in utterance: 622
[ INFO ] Average Infer time per frame: 4.59ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.7389560
[ INFO ] avg error: 0.0465543
[ INFO ] avg rms error: 0.0604941
[ INFO ] stdev error: 0.0386294
[ INFO ]
[ INFO ] Utterance 8:
[ INFO ] Total time in Infer (HW and SW): 2493.28ms
[ INFO ] Frames in utterance: 548
[ INFO ] Average Infer time per frame: 4.55ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.6680136
[ INFO ] avg error: 0.0439341
[ INFO ] avg rms error: 0.0574614
[ INFO ] stdev error: 0.0370353
[ INFO ]
[ INFO ] Utterance 9:
[ INFO ] Total time in Infer (HW and SW): 1654.67ms
[ INFO ] Frames in utterance: 368
[ INFO ] Average Infer time per frame: 4.50ms
[ INFO ]
[ INFO ] Output blob name: affinetransform14
[ INFO ] Number scores per frame: 3425
[ INFO ]
[ INFO ] max error: 0.6550579
[ INFO ] avg error: 0.0467643
[ INFO ] avg rms error: 0.0605045
[ INFO ] stdev error: 0.0383914
[ INFO ]
[ INFO ] Total sample time: 39722.60ms
[ INFO ] File result.npz was created!
[ INFO ] This sample is an API example, for any performance measurements please use the dedicated benchmark_app tool

Automatic Speech Recognition Python* Sample¶

How It Works¶

GNA-specific details¶

Quantization¶

Execution Modes¶

Loading and Saving Models¶

Running¶

Model Preparation¶

Speech Inference¶

Sample Output¶

See Also¶