clipper/backend/youtube/helpers.go

package youtube

import (
	"fmt"
	"sort"
	"strings"

	youtubev2 "github.com/kkdai/youtube/v2"
)

func FormatDebugString(format *youtubev2.Format, includeURL bool) string {
	var url string
	if includeURL {
		url = format.URL
	}
	return fmt.Sprintf(
		"iTag = %d, mime_type = %s, quality = %s, quality_label = %s, bitrate = %d, fps = %d, width = %d, height = %d, content_length = %d, duration = %v, audio_channels = %d, audio_sample_rate = %s, audio_quality = %s, url = %s",
		format.ItagNo,
		format.MimeType,
		format.Quality,
		format.QualityLabel,
		format.Bitrate,
		format.FPS,
		format.Width,
		format.Height,
		format.ContentLength,
		format.ApproxDurationMs,
		format.AudioChannels,
		format.AudioSampleRate,
		format.AudioQuality,
		url,
	)
}

// SortAudio returns the provided formats ordered in descending preferred
// order. The ideal candidate is 44.1kHz stereo audio in a webm container, with
// the highest available bitrate.
func SortAudio(inFormats youtubev2.FormatList) youtubev2.FormatList {
	// TODO: sort in-place.
	var formats youtubev2.FormatList
	for _, format := range inFormats {
		if format.FPS == 0 && format.AudioChannels > 0 {
			formats = append(formats, format)
		}
	}
	sort.SliceStable(formats, func(i, j int) bool {
		isOpusI := strings.Contains(formats[i].MimeType, "opus")
		isOpusJ := strings.Contains(formats[j].MimeType, "opus")
		if isOpusI && isOpusJ {
			isStereoI := formats[i].AudioChannels == 2
			isStereoJ := formats[j].AudioChannels == 2
			if isStereoI && isStereoJ {
				is48kI := formats[i].AudioSampleRate == "48000"
				is48kJ := formats[j].AudioSampleRate == "48000"
				if is48kI && is48kJ {
					return formats[i].Bitrate > formats[j].Bitrate
				}
				return is48kI
			}
			return isStereoI
		}
		return isOpusI
	})
	return formats
}

// SortVideo returns the provided formats ordered in descending preferred
// order. The ideal candidate is video in an mp4 container with a medium
// bitrate, with audio channels (needed to allow synced playback on the
// website).
func SortVideo(inFormats youtubev2.FormatList) youtubev2.FormatList {
	// TODO: sort in-place.
	var formats youtubev2.FormatList
	for _, format := range inFormats {
		if format.FPS > 0 && format.AudioChannels > 0 {
			formats = append(formats, format)
		}
	}
	sort.SliceStable(formats, func(i, j int) bool {
		isMP4I := strings.Contains(formats[i].MimeType, "mp4")
		isMP4J := strings.Contains(formats[j].MimeType, "mp4")
		if isMP4I && isMP4J {
			return compareQualityLabel(formats[i].QualityLabel, formats[j].QualityLabel)
		}
		return strings.Contains(formats[i].MimeType, "mp4")
	})
	return formats
}

func compareQualityLabel(a, b string) bool {
	return (a == "360p" || a == "480p") && (b != "360p" && b != "480p")
}