Maksim Totmin
4c34f0bedc
Streams H.264 to the Galahad II LCD via USB (gousb) with: - ffmpeg CLI transcoding (no fragile FFmpeg C-ABI bindings) - pure-Go Annex-B access-unit splitting - framerate pacing with graceful shutdown and USB reconnect - TOML config, cobra CLI, structured slog logging, unit tests
65 lines
1.7 KiB
Go
65 lines
1.7 KiB
Go
// Package protocol builds the USB packets that the Lian Li Galahad II LCD
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// expects. It is a pure, dependency-free implementation of the framing used
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// by the reference Rust/Python drivers.
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//
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// Each H.264 frame is split into one or more 512-byte USB packets. Every
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// packet carries an 11-byte header:
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//
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// [0] report_id (0x02)
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// [1] command (0x0D = send H.264)
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// [2:6] total payload size (big-endian)
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// [6:9] packet index, 3 bytes (big-endian, wraps)
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// [9:11] chunk length in this packet (big-endian)
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//
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// followed by up to 501 bytes of frame data and zero padding.
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package protocol
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import (
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"encoding/binary"
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"fmt"
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)
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// Wire-level constants shared with the reference implementation.
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const (
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ReportIDVideo = 0x02
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CmdSendH264 = 0x0D
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HeaderSize = 11
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PacketSize = 512
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MaxPayloadSize = 501
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)
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// EncodePackets splits frame data into USB packets. It returns an error only
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// when frame is empty, which would otherwise produce a malformed stream.
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func EncodePackets(frame []byte) ([][]byte, error) {
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if len(frame) == 0 {
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return nil, fmt.Errorf("cannot encode empty frame")
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}
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var packets [][]byte
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for offset, idx := 0, uint32(0); offset < len(frame); offset += MaxPayloadSize {
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end := min(offset+MaxPayloadSize, len(frame))
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chunk := frame[offset:end]
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pkt := make([]byte, PacketSize)
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pkt[0] = ReportIDVideo
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pkt[1] = CmdSendH264
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binary.BigEndian.PutUint32(pkt[2:6], uint32(len(frame)))
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pkt[6] = byte(idx >> 16)
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pkt[7] = byte(idx >> 8)
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pkt[8] = byte(idx)
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binary.BigEndian.PutUint16(pkt[9:11], uint16(len(chunk)))
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copy(pkt[HeaderSize:HeaderSize+len(chunk)], chunk)
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packets = append(packets, pkt)
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idx++
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}
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return packets, nil
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}
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func min(a, b int) int {
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if a < b {
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return a
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}
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return b
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}
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