KaraZajac
105 lines
5.6 KiB
Markdown
105 lines
5.6 KiB
Markdown
# Sub Decode: ProtoPirate vs KAT
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Comparison of how **ProtoPirate** (REFERENCES/protopirate) and **KAT** decode Flipper `.sub` (RAW) files.
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## File format
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Both use the same Flipper SubGhz RAW format:
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- **Filetype:** `Flipper SubGhz RAW File`
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- **Protocol:** `RAW`
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- **Frequency:** one value (Hz)
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- **RAW_Data:** space-separated **int32** values:
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- **Positive** = HIGH level
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- **Negative** = LOW level
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- **Magnitude** = duration in **microseconds**
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So parsing and (level, duration) stream content are the same.
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---
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## ProtoPirate sub decode (REFERENCES/protopirate)
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### Where it lives
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- **Scene:** `scenes/protopirate_scene_sub_decode.c`
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- **Raw reader:** `helpers/raw_file_reader.c` / `raw_file_reader.h`
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### Flow
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1. **Open file**
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`raw_file_reader_open()` uses FlipperFormat to open the file, checks header "Flipper SubGhz RAW File" and Protocol "RAW". Does **not** read Frequency in the reader; the scene reads that separately.
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2. **Read metadata (scene)**
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In `DecodeStateReadHeader` / `DecodeStateStartingWorker` the scene opens the file again with FlipperFormat and reads:
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- **Frequency** (default 433920000 if missing)
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- **Preset** (e.g. AM650, FM238) and maps it to the SubGhz preset used for the receiver.
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3. **Feed stream**
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In `DecodeStateDecodingRaw`:
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- Loop: `raw_file_reader_get_next(ctx->raw_reader, &level, &duration)` to get the next (level, duration).
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- For each pair: **`subghz_receiver_decode(app->txrx->receiver, level, duration)`**.
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- Reads in chunks of **128** samples per tick (`SAMPLES_TO_READ_PER_TICK`) for UI responsiveness.
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4. **On decode**
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When the Flipper receiver reports a decode (`protopirate_sub_decode_receiver_callback`):
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- Add the decode to history.
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- **`subghz_receiver_reset(receiver)`** so all decoders are reset.
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- Continue feeding the **same** file from the next sample.
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So: one continuous stream from the file, (level, duration) in order; on each decode → record → reset receiver → keep going. **No** polarity inversion in this path. **No** sliding window or multiple start positions.
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### Raw file reader details
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- **`raw_file_reader_get_next()`** (raw_file_reader.c):
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Reads next int32 from buffer; if buffer is empty, loads next chunk via `flipper_format_read_int32(..., "RAW_Data", ...)`.
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`level = (value >= 0)`, `duration = abs(value)`. Same convention as KAT.
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---
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## KAT sub import (src/app.rs + protocols/mod.rs + export/flipper.rs)
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### Where it lives
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- **Import:** `src/export/flipper.rs` → `import_sub_raw(path)` → returns `(frequency, Vec<StoredLevelDuration>)`.
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- **Decode:** `src/protocols/mod.rs` → `process_signal_stream()` / `process_signal_stream_inner()`.
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- **Use:** `src/app.rs` → when loading a .sub file, calls `import_sub_raw` then `protocols.process_signal_stream(&pairs, frequency)`.
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### Flow
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1. **Parse file**
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`import_sub_raw()`:
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- Reads whole file as text.
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- Parses **Frequency** (default 433_920_000 if missing).
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- Parses all **RAW_Data** lines into one list of (level, duration) with the same rule: positive ⇒ HIGH, negative ⇒ LOW, duration = abs(value) µs.
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2. **Decode stream**
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`process_signal_stream(pairs, frequency)`:
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- Tries **normal polarity** first: `process_signal_stream_inner(pairs, frequency, false)`.
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- If that returns **no** decodes, tries **inverted polarity**: `process_signal_stream_inner(pairs, frequency, true)` (flip level for every pair).
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- Inner loop: for each (level, duration) in order, for each decoder that supports the file frequency, call **`decoder.feed(level, duration_us)`**. If any decoder returns a decode:
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- Record (protocol name, decoded signal, segment of pairs).
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- **Reset all decoders** and set `segment_start` to next index.
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- Continue from the next pair.
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So: one pass over the in-memory stream; on each decode → record → reset all decoders → continue. **Difference:** KAT also runs a **second** pass with **inverted polarity** if the first pass finds nothing.
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---
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## Differences summary
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| Aspect | ProtoPirate | KAT |
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|--------|-------------|-----|
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| **File format** | Same (Flipper RAW, positive=HIGH, negative=LOW, µs) | Same |
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| **Stream order** | Same (sequential level/duration from file) | Same |
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| **Frequency** | Read from file, used for preset/receiver | Read from file, used for decoder filter (2% tolerance) |
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| **Decode loop** | One (level, duration) at a time → `subghz_receiver_decode()` | One (level, duration) at a time → `decoder.feed()` for each decoder |
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| **On decode** | Add to history, **subghz_receiver_reset()**, continue same file | Append to list, **reset all decoders**, continue same stream |
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| **Polarity** | Single polarity (as in file) | Tries **normal**, then **inverted** if no decodes |
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| **Sliding window / multiple starts** | No | No |
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| **“No protocol” result** | Shows “No ProtoPirate protocol detected” (no “Unknown” capture) | No capture if no decoder ever returns (same idea) |
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So the **sub decode strategy is the same**: single stream, reset-after-each-decode, no sliding window. The only functional difference is **KAT’s extra inverted-polarity pass** when the normal pass finds no decodes.
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For a file like the VAG Suran .sub: the first HIGH pulse is 133 µs, so VAG’s Reset condition (300±79 or 500±79 µs) is never met. In both codebases the decoder would stay in Reset and never emit a decode; neither would create a capture from that stream. ProtoPirate would show “No ProtoPirate protocol detected”; KAT would add no capture. So for that case the behavior is aligned; fixing it would require something like trying decode from multiple start indices (sliding window) or trimming to the first VAG-like preamble, in either codebase.
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