feat: parse analog_in_data_ts for batched PB streaming messages

[cptkoolbeenz]

Context

The firmware is adding batched PB streaming (daqifi/daqifi-nyquist-firmware#238) to improve throughput by packing multiple sample sets into a single protobuf message. This requires the desktop app to parse the analog_in_data_ts field to reconstruct per-sample-set timestamps.

Current Behavior

Each PB streaming message contains one sample set:

• msg_time_stamp = timestamp for this sample set
• analog_in_data = channel values (count = enabled channels)
• analog_in_data_ts = empty (count=0, unused)

New Behavior (after firmware #238)

Each PB message may contain multiple sample sets batched together:

• msg_time_stamp = first sample set's timestamp (base)
• analog_in_data_ts = one timestamp per sample set (absolute or offset from base)
• analog_in_data = all values concatenated (count = N sample sets × enabled channels)

Example (3 sample sets, 4 channels enabled):

msg_time_stamp: 1000000
analog_in_data_ts: [1000000, 1000100, 1000200]
analog_in_data: [v0, v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11]

The app should chunk analog_in_data by the known channel count (analog_in_port_num) and assign each chunk the corresponding analog_in_data_ts entry.

Required Changes

In daqifi-core (ProtobufProtocolHandler or equivalent message parser):

1. When AnalogInDataTs has entries (Count > 0):

   • Determine samples per set from AnalogInPortNum (channel count from initial info message)
   • Chunk AnalogInData into groups of channelCount values
   • Assign each group the timestamp from AnalogInDataTs[groupIndex]

2. When AnalogInDataTs is empty (Count == 0):

   • Current behavior unchanged (one sample set per message, use MsgTimeStamp)

Backward Compatibility

• Messages without analog_in_data_ts work exactly as before
• The app should handle both batched and non-batched messages seamlessly
• No proto file changes needed — analog_in_data_ts (field 4) already exists in the proto3 schema

Performance Impact

Firmware benchmarks show batching improves PB streaming ceilings:

• USB PB 1ch: 18kHz → 20kHz
• USB PB 16ch: 5kHz → 7kHz
• 15-39% fewer bytes per sample (reduced framing overhead)

Related

• perf: batch PB streaming with per-sample-set timestamps via analog_in_data_ts daqifi-nyquist-firmware#238 (firmware batching implementation)
• perf(streaming): benchmark mode, encoder optimization, proto3 migration (#233, #235, #236) daqifi-nyquist-firmware#237 (PR with fast encoder infrastructure)
• Improve protobuf protocol to use self-describing channel data format daqifi-nyquist-firmware#62 (self-describing protobuf format)