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// Package transcode implements routines for transcoding to various kinds of
// receiver.
package transcode
import (
"io"
"os/exec"
"runtime"
"strconv"
"time"
"github.com/anacrolix/log"
. "github.com/anacrolix/dms/misc"
"github.com/anacrolix/ffprobe"
)
// Invokes an external command and returns a reader from its stdout. The
// command is waited on asynchronously.
func transcodePipe(args []string, stderr io.Writer) (r io.ReadCloser, err error) {
log.Println("transcode command:", args)
cmd := exec.Command(args[0], args[1:]...)
cmd.Stderr = stderr
r, err = cmd.StdoutPipe()
if err != nil {
return
}
err = cmd.Start()
if err != nil {
return
}
go func() {
err := cmd.Wait()
if err != nil {
log.Printf("command %s failed: %s", args, err)
}
}()
return
}
// Return a series of ffmpeg arguments that pick specific codecs for specific
// streams. This requires use of the -map flag.
func streamArgs(s map[string]interface{}) (ret []string) {
defer func() {
if len(ret) != 0 {
ret = append(ret, []string{
"-map", "0:" + strconv.Itoa(int(s["index"].(float64))),
}...)
}
}()
switch s["codec_type"] {
case "video":
/*
if s["codec_name"] == "h264" {
if i, _ := strconv.ParseInt(s["is_avc"], 0, 0); i != 0 {
return []string{"-vcodec", "copy", "-sameq", "-vbsf", "h264_mp4toannexb"}
}
}
*/
return []string{"-target", "pal-dvd"}
case "audio":
if s["codec_name"] == "dca" {
return []string{"-acodec", "ac3", "-ab", "224k", "-ac", "2"}
} else {
return []string{"-acodec", "copy"}
}
case "subtitle":
return []string{"-scodec", "copy"}
}
return
}
// Streams the desired file in the MPEG_PS_PAL DLNA profile.
func Transcode(path string, start, length time.Duration, stderr io.Writer) (r io.ReadCloser, err error) {
args := []string{
"ffmpeg",
"-threads", strconv.FormatInt(int64(runtime.NumCPU()), 10),
"-async", "1",
"-ss", FormatDurationSexagesimal(start),
}
if length >= 0 {
args = append(args, []string{
"-t", FormatDurationSexagesimal(length),
}...)
}
args = append(args, []string{
"-i", path,
}...)
info, err := ffprobe.Run(path)
if err != nil {
return
}
for _, s := range info.Streams {
args = append(args, streamArgs(s)...)
}
args = append(args, []string{"-f", "mpegts", "pipe:"}...)
return transcodePipe(args, stderr)
}
// Returns a stream of Chromecast supported VP8.
func VP8Transcode(path string, start, length time.Duration, stderr io.Writer) (r io.ReadCloser, err error) {
args := []string{
"avconv",
"-threads", strconv.FormatInt(int64(runtime.NumCPU()), 10),
"-async", "1",
"-ss", FormatDurationSexagesimal(start),
}
if length > 0 {
args = append(args, []string{
"-t", FormatDurationSexagesimal(length),
}...)
}
args = append(args, []string{
"-i", path,
// "-deadline", "good",
// "-c:v", "libvpx", "-crf", "10",
"-f", "webm",
"pipe:",
}...)
return transcodePipe(args, stderr)
}
// Returns a stream of Chromecast supported matroska.
func ChromecastTranscode(path string, start, length time.Duration, stderr io.Writer) (r io.ReadCloser, err error) {
args := []string{
"ffmpeg",
"-ss", FormatDurationSexagesimal(start),
"-i", path,
"-c:v", "libx264", "-preset", "ultrafast", "-profile:v", "high", "-level", "5.0",
"-movflags", "+faststart+frag_keyframe+empty_moov",
}
if length > 0 {
args = append(args, []string{
"-t", FormatDurationSexagesimal(length),
}...)
}
args = append(args, []string{
"-f", "mp4",
"pipe:",
}...)
return transcodePipe(args, stderr)
}
// Returns a stream of h264 video and mp3 audio
func WebTranscode(path string, start, length time.Duration, stderr io.Writer) (r io.ReadCloser, err error) {
args := []string{
"ffmpeg",
"-ss", FormatDurationSexagesimal(start),
"-i", path,
"-pix_fmt", "yuv420p",
"-c:v", "libx264", "-crf", "25",
"-c:a", "mp3", "-ab", "128k", "-ar", "44100",
"-preset", "ultrafast",
"-movflags", "+faststart+frag_keyframe+empty_moov",
}
if length > 0 {
args = append(args, []string{
"-t", FormatDurationSexagesimal(length),
}...)
}
args = append(args, []string{
"-f", "mp4",
"pipe:",
}...)
return transcodePipe(args, stderr)
}
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