chore: import upstream snapshot with attribution

tools/speech_data_explorer/README.md

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+Speech Data Explorer
+--------------------
+
+[Dash](https://plotly.com/dash/)-based tool for interactive exploration of ASR/TTS datasets.
+
+Features:
+- dataset's statistics (alphabet, vocabulary, duration-based histograms)
+- navigation across dataset (sorting, filtering)
+- inspection of individual utterances (waveform, spectrogram, audio player)
+- errors' analysis (Word Error Rate, Character Error Rate, Word Match Rate, Mean Word Accuracy, diff)
+- comparison of two ASR models using interactive word-level accuracy plot
+- read manifests and audio directly from S3-compatible storage (including AIStore)
+- support for tarred audio datasets with efficient byte-range reads via DALI index files
+
+## Quick Start
+
+Install the requirements:
+```
+pip install -r requirements.txt
+```
+
+Run with a local manifest:
+```
+python data_explorer.py path_to_manifest.json
+```
+
+## S3 / AIStore Support
+
+Speech Data Explorer can read manifests and audio files directly from S3-compatible
+object storage, including NVIDIA AIStore (AIS).
+
+### Using an S3 config file
+
+```
+python data_explorer.py s3://bucket/manifest.json --s3cfg ~/.s3cfg[default]
+```
+
+### Using AIStore with environment variables
+
+```
+export AIS_ENDPOINT=http://ais-gateway:8080
+export AIS_AUTHN_TOKEN=your_token
+python data_explorer.py s3://bucket/manifest.json --s3cfg AIS
+```
+
+### Sharded paths (`_OP_/_CL_` syntax)
+
+Manifests and tar files are often split into numbered shards. Instead of listing
+every shard explicitly, use the `_OP_start..end_CL_` range pattern. The tool
+expands it into individual paths automatically:
+
+```
+s3://bucket/manifest__OP_0..255_CL_.json
+→  s3://bucket/manifest_0.json
+   s3://bucket/manifest_1.json
+   ...
+   s3://bucket/manifest_255.json
+```
+
+Multiple ranges in a single path produce a **cartesian product** — useful when
+shards are spread across several buckets or directories:
+
+```
+s3://store_OP_1..2_CL_/audio__OP_0..1_CL_.tar
+→  s3://store1/audio_0.tar
+   s3://store1/audio_1.tar
+   s3://store2/audio_0.tar
+   s3://store2/audio_1.tar
+```
+
+### Tarred audio
+
+When audio is stored in tar archives locally or on S3, use `--tar-base-path` to
+point to the tar files. DALI index files are used automatically (if available at
+`<tar_dir>/dali_index/`) for fast byte-range lookups:
+
+```
+python data_explorer.py /data/manifests/manifest.json \
+    --tar-base-path /data/tarred/audio.tar
+```
+
+```
+python data_explorer.py s3://bucket/manifests/manifest__OP_0..255_CL_.json \
+    --tar-base-path s3://bucket/tarred/audio__OP_0..255_CL_.tar \
+    --s3cfg ~/.s3cfg[default]
+```
+
+You can also specify a custom DALI index location:
+```
+python data_explorer.py s3://bucket/manifest.json \
+    --tar-base-path s3://bucket/tarred/audio__OP_0..255_CL_.tar \
+    --dali-index-base s3://bucket/tarred/dali_index/ \
+    --s3cfg ~/.s3cfg[default]
+```
+
+## Comparing Two ASR Models
+
+### Single manifest with two prediction fields
+
+If your manifest contains two `pred_text_*` fields (e.g. `pred_text_contextnet`
+and `pred_text_conformer`):
+
+```
+python data_explorer.py path_to_manifest.json \
+    -nc pred_text_contextnet pred_text_conformer
+```
+
+### Two separate manifests
+
+You can also pass two separate manifests (order-invariant). Each manifest must
+contain a plain `pred_text` field, and `-nc` names the models:
+
+```
+python data_explorer.py manifest_model_A.json manifest_model_B.json \
+    -nc pred_text_model_A pred_text_model_B
+```
+
+## Manifest Format
+
+JSON manifest file should contain the following fields:
+- `audio_filepath` — path to audio file (local path, or filename inside a tar archive when using `--tar-base-path`)
+- `duration` — duration of the audio file in seconds
+- `text` — reference transcript
+
+Errors' analysis requires `pred_text` (ASR transcript) for all utterances.
+
+Any additional field will be parsed and displayed in the Samples tab.
+
+## Additional Options
+
+| Flag | Description |
+|------|-------------|
+| `--vocab` | Vocabulary file to highlight OOV words |
+| `--port` | Serving port (default: 8050) |
+| `--estimate-audio-metrics` / `-a` | Estimate audio metrics |
+| `--base-path` | Base path for relative audio paths in the manifest |
+| `--tar-base-path` | Local or S3 path to tarred audio files (supports sharded `_OP_..._CL_` patterns) |
+| `--dali-index-base` | Local or S3 path to DALI index directory for fast tar lookups |
+| `--s3cfg` / `-s3c` | S3 config file and section, or `AIS` for AIStore env vars |
+| `--force` / `-f` | Tolerate manifest entries with missing required fields |
+| `-nc` / `--names_compared` | Two field names for model comparison |
+| `--show_statistics` / `-shst` | Field name to show statistics for |
+| `--debug` / `-d` | Enable debug mode |
+
+![Speech Data Explorer](screenshot.png)

tools/speech_data_explorer/requirements.txt

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+boto3
+braceexpand
+dash>=2.1.0
+dash_bootstrap_components>=1.0.3
+diff_match_patch
+kaldialign
+librosa>=0.9.1
+numpy
+pandas
+plotly
+requests
+SoundFile
+tqdm