Decoder Module (`src/decoder.rs`)

The Decoder reverses the process, reading a video stream and reconstructing the original binary file.

Workflow

mermaid

graph TD
    A[Video File] -->|FFmpeg| B[Raw Frames]
    B -->|Block Scan| C[Recover Bits]
    C -->|Assemble| D[Shards Buffer]
    D -->|Accumulate| E{Check if Full?}
    E -->|No| B
    E -->|Yes| F[Reed-Solomon Reconstruct]
    F -->|Write Data| G[Output File]

Key Logic

1. Header Bootstrap

The first frame is special. It contains the FileHeader. Challenge: To read the header, we need to know the Block Size. Solution: The header is ALWAYS encoded with a fixed Block Size = 4. This allows the decoder to reliably "bootstrap" itself without knowing user settings beforehand.

2. Reconstruction

We read frames sequentially. Since we use ffv1 (lossless) or assume good transmission, we typically get valid data.

rust

// If we had missing frames, RS would fill in the gaps here
rs.reconstruct(&mut shards_buffer)?;

3. Integrity Check

We calculate the SHA256 of the output file on-the-fly. At the end, the hash is printed to stdout. If the header's sha256_hash field is not PENDING, the decoder compares the two values and warns if they differ. In practice, the header hash is currently always set to PENDING by the encoder, so automatic integrity verification is not performed; keep the hash printed at encode time separately if you need it.

Decoder Module (src/decoder.rs) ​

Workflow ​

Key Logic ​

1. Header Bootstrap ​