midi: fixed lint warnings

Author: twystd

README.md

@@ -110,6 +110,7 @@ jsonl,
 macho_fat,
 [markdown](doc/formats.md#markdown),
 [matroska](doc/formats.md#matroska),
+[midi](doc/formats.md#midi),
 [moc3](doc/formats.md#moc3),
 [mp3](doc/formats.md#mp3),
 mp3_frame,

doc/formats.md

@@ -82,6 +82,7 @@
 |`macho_fat`                                                     |Fat&nbsp;Mach-O&nbsp;macOS&nbsp;executable&nbsp;(multi-architecture)                                         |<sub>`macho`</sub>|
 |[`markdown`](#markdown)                                         |Markdown                                                                                                     |<sub></sub>|
 |[`matroska`](#matroska)                                         |Matroska&nbsp;file                                                                                           |<sub>`aac_frame` `av1_ccr` `av1_frame` `avc_au` `avc_dcr` `flac_frame` `flac_metadatablocks` `hevc_au` `hevc_dcr` `image` `mp3_frame` `mpeg_asc` `mpeg_pes_packet` `mpeg_spu` `opus_packet` `vorbis_packet` `vp8_frame` `vp9_cfm` `vp9_frame`</sub>|
+|[`midi`](#midi)                                                 |Standard&nbsp;MIDI&nbsp;file                                                                                 |<sub></sub>|
 |[`moc3`](#moc3)                                                 |MOC3&nbsp;file                                                                                               |<sub></sub>|
 |[`mp3`](#mp3)                                                   |MP3&nbsp;file                                                                                                |<sub>`id3v2` `id3v1` `id3v11` `apev2` `mp3_frame`</sub>|
 |`mp3_frame`                                                     |MPEG&nbsp;audio&nbsp;layer&nbsp;3&nbsp;frame                                                                 |<sub>`mp3_frame_tags`</sub>|
@@ -867,6 +868,43 @@ $ fq 'grep_by(.id == "Tracks") | matroska_path' file.mkv
 - https://www.matroska.org/technical/codec_specs.html
 - https://wiki.xiph.org/MatroskaOpus
 
+## midi
+Standard MIDI file.
+
+### Notes
+
+1. Only supports the MIDI 1.0 specification.
+2. Does only basic validation on the MIDI data.
+
+### Sample queries
+
+1. Extract the track names from a MIDI file
+```
+fq -d midi -d midi '.. | select(.event=="Track Name")? | "\(.name)"' twinkle.mid 
+```
+
+2. Extract the tempo changes from a MIDI file
+```
+fq -d midi '.. | select(.event=="Tempo")?.tempo' twinkle.mid
+```
+
+3. Extract the key changes from a MIDI file
+```
+fq -d midi '.. | select(.event=="Key Signature")?.key' key-signatures.mid
+```
+
+4. Extract NoteOn and NoteOff events:
+```
+fq -d midi 'grep_by(.event=="Note On" or .event=="Note Off") | "\(.event)  \(.time.tick)  \(.note)"' twinkle.mid
+```
+
+### Authors
+- transcriptaze.development@gmail.com
+
+### References
+
+1. [The Complete MIDI 1.0 Detailed Specification](https://www.midi.org/specifications/item/the-midi-1-0-specification)
+
 ## moc3
 MOC3 file.
 

format/midi/.gitignore

@@ -1,5 +1,5 @@
 .DS_Store
 workdir
 Makefile
-Makefile.midi
+TODO.md
 

format/midi/controllers.go

@@ -67,7 +67,7 @@ var controllers = scalar.UintMapSymStr{
 	84: "Portamento Control",
 	88: "High Resolution Velocity Prefix",
 	91: "Effects 1 Depth (Reverb Send Level)",
-	92: "Effects 2 Depth (Tremelo Depth)",
+	92: "Effects 2 Depth (Tremolo Depth)",
 	93: "Effects 3 Depth (Chorus Send Level)",
 	94: "Effects 4 Depth (Celeste Depth)",
 	95: "Effects 5 Depth (Phaser Depth)",

format/midi/midi.go

@@ -84,14 +84,12 @@ func decodeMThd(d *decode.D) {
 			division := d.FieldU16("divisions")
 			if division&0x8000 == 0x8000 {
 				SMPTE := (division & 0xff00) >> 8
-				if SMPTE != 0xe8 && SMPTE != SMPTE && SMPTE != 0xe6 && SMPTE != 0xe5 {
+				if SMPTE != 0xe8 && SMPTE != 0xe7 && SMPTE != 0xe6 && SMPTE != 0xe5 {
 					d.Errorf("invalid MThd division SMPTE timecode type %02X (expected E8,E7, E6 or E5)", SMPTE)
 				}
 			}
 		})
 	})
-
-	return
 }
 
 func decodeMTrk(d *decode.D) {
@@ -140,23 +138,21 @@ func skipTo(d *decode.D, tag string) error {
 		if string(bytes[0:4]) == tag {
 			return nil
 		} else {
-			len := 8 + binary.BigEndian.Uint32(bytes[4:])
+			length := 8 + binary.BigEndian.Uint32(bytes[4:])
 
-			d.SeekRel(8 * int64(len))
+			d.SeekRel(8 * int64(length))
 		}
 	}
 
 	return fmt.Errorf("missing %v chunk", tag)
 }
 
 func peekEvent(d *decode.D) (uint64, uint8, uint8) {
-	delta := uint64(0)
-	N := 3
+	var delta uint64
+	var N int = 3
 
 	for {
 		bytes := d.PeekBytes(N)
-
-		// ... peek at delta value
 		delta = 0
 
 		for i, b := range bytes[:N-2] {