108 lines
2.6 KiB
Go
108 lines
2.6 KiB
Go
package media
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import (
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"bytes"
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"context"
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"errors"
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"log/slog"
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"os"
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"os/exec"
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"strings"
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)
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func IsIOSPlayableMime(mime string) bool {
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switch mime {
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case "video/mp4", "video/quicktime", "audio/mp4", "audio/aac", "audio/x-m4a", "audio/mpeg":
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return true
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}
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return false
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}
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func IsAudio(mime string) bool {
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return strings.HasPrefix(mime, "audio/")
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}
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type TranscodeInput struct {
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SourceURL string
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MimeType string
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}
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type TranscodeOutput struct {
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TempLocalFilePath string
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OutputMimeType string
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// Extension such as ".m4a" or ".mp4"
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OutputExt string
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}
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var (
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ErrInvalidInput error = errors.New("invalid input")
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)
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// TranscodeToMp4 takes in any audio or video source URL and
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// returns the filepath of the transcoded media
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// WARNING: caller responsible for deleting TempLocalFilePath
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func TranscodeToMp4(ctx context.Context, input TranscodeInput) (*TranscodeOutput, error) {
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if input.SourceURL == "" || input.MimeType == "" {
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return nil, ErrInvalidInput
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}
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isAudio := IsAudio(input.MimeType)
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var outputExt, outputMime string
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if isAudio {
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outputExt = ".m4a"
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outputMime = "audio/mp4"
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} else {
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outputExt = ".mp4"
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outputMime = "video/mp4"
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}
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tmp, err := os.CreateTemp("", "transcode-*"+outputExt)
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if err != nil {
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slog.Error("transcode: failed to create temp file", "error", err)
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return nil, err
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}
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tmpPath := tmp.Name()
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tmp.Close()
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var args []string
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if isAudio {
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args = []string{
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"-y", "-i", input.SourceURL,
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"-vn",
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"-c:a", "aac", "-b:a", "128k",
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"-movflags", "+faststart",
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tmpPath,
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}
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} else {
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// Cap encoder parallelism and lookahead to keep memory bounded — screen
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// recordings come in at native display resolution (often 1440p–4K) and
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// libx264's per-thread lookahead/reference buffers blow past the worker's
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// memory limit otherwise. Output is also downscaled to 1080p max, which
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// mobile playback won't notice; the original WebM stays in GCS untouched.
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args = []string{
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"-y", "-i", input.SourceURL,
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"-vf", "scale='min(1920,iw)':-2:flags=lanczos",
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"-c:v", "libx264", "-preset", "veryfast", "-crf", "23",
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"-pix_fmt", "yuv420p", "-profile:v", "baseline", "-level", "3.1",
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"-x264-params", "rc-lookahead=20:ref=2",
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"-threads", "2", "-filter_threads", "2",
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"-c:a", "aac", "-b:a", "128k",
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"-movflags", "+faststart",
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tmpPath,
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}
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}
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cmd := exec.CommandContext(ctx, "ffmpeg", args...)
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var stderr bytes.Buffer
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cmd.Stderr = &stderr
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if err := cmd.Run(); err != nil {
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return nil, errors.Join(err, errors.New(stderr.String()))
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}
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return &TranscodeOutput{
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TempLocalFilePath: tmpPath,
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OutputMimeType: outputMime,
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OutputExt: outputExt,
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}, nil
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}
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