| --- |
| license: cc-by-nc-4.0 |
| task_categories: |
| - automatic-speech-recognition |
| - text-to-speech |
| language: |
| - en |
| --- |
| |
| # CC3M spoken captions (image–speech) — DualCodec pre-tokenized |
|
|
| DualCodec (12 Hz) pre-tokenized speech for omni speech–vision MLLM training. |
| Source: Conceptual Captions 3M (filtered); speech synthesized with CosyVoice2. |
|
|
| ## Contents (train split) |
|
|
| | | | |
| |---|---| |
| | **Total samples** | ≈ 500,000 (image–caption–speech triples) | |
| | **Total audio** | ≈ 735 hours | |
| | **WebDataset shards** | see repo (`.tar`) | |
| | **Mean / median duration** | 5.29s / 4.92s | |
| | **p90 / max duration** | 8.08s / 25.67s | |
| | **Length cap** | 30s | |
|
|
| *Counts/hours are computed by sampling shards (per-shard sample count × #shards); duration stats from a scanned subset.* |
|
|
| ### Duration distribution |
| | bucket | share | |
| |---|---| |
| | 0-5s | 51.3% | |
| | 5-10s | 44.9% | |
| | 10-15s | 3.5% | |
| | 15-20s | 0.2% | |
| | >20s | 0.0% | |
|
|
| ## Format (WebDataset `.tar`) |
|
|
| Each sample shares a key and consists of `{key}.sem.npy`, `{key}.ac.npy`, `{key}.txt`, `{key}.jpg`: |
| - **`.sem.npy`** — DualCodec **semantic** codes, `int16`, shape `(T,)`, vocab 16384. |
| - **`.ac.npy`** — DualCodec **acoustic** codes, `int16`, shape `(7, T)`, vocab 4096 per codebook. |
| - **`.txt`** — spoken caption text. |
| - **Image** (`.jpg`): RGB 256×256, joined from the source image corpus by sample key. |
|
|
| Frame rate is **12 Hz**, so duration in seconds = `T / 12`. |
|
|
| ## Length & padding |
|
|
| Codes are stored at their **true variable length** (no padding baked in). Samples |
| longer than the training grid are handled at load time. During training, sequences |
| are padded to a fixed **240-frame (20 s) grid** by appending the DualCodec |
| **encoded-silence column** (semantic code **3716**, with its matching acoustic |
| column) — i.e. padding is applied as *code-level silence*, not waveform zeros, so |
| the padded region matches the codec's silence distribution. Samples exceeding the |
| grid (> 240 frames) are skipped rather than cropped to preserve audio–text alignment. |
|
|
| ## Intended use |
|
|
| image→speech (i2s) and speech→image (s2i) alignment SFT. Semantic + acoustic codes reconstruct waveforms via the DualCodec decoder. |
|
|
