ffmpeg: Add transcoder example program.

Includes support to toggle GPU via CLI flags.

Also update documentation.

README.md

@@ -131,4 +131,39 @@ To handle HLS playback:
 		})
 ```
 
+### GPU Support
+
+Processing on Nvidia GPUs is supported. To enable this capability, FFmpeg needs
+to be built with GPU support. See the
+[FFmpeg guidelines](https://trac.ffmpeg.org/wiki/HWAccelIntro#NVENCNVDEC) on
+this.
+
+To execute the nvidia tests within the `ffmpeg` directory, run this command:
+
+```
+go test -tag=nvidia -run Nvidia
+
+```
+
+To run the tests on a particular GPU, use the GPU_DEVICE environment variable:
+
+```
+# Runs on GPU number 3
+GPU_DEVICE=3 go test -tag nvidia -run Nvidia
+```
+
+Aside from the tests themselves, there is a
+[sample program](https://github.com/livepeer/lpms/blob/master/cmd/transcoding/transcoding.go)
+that can be used as a reference to the LPMS GPU transcoding API. The sample
+program can select GPU or software processing via CLI flags. Run the sample
+program via:
+
+```
+# software processing
+go run cmd/transcoding/transcoding.go transcoder/test.ts P144p30fps16x9,P240p30fps16x9 sw
+
+# nvidia processing, GPU number 2
+go run cmd/transcoding/transcoding.go transcoder/test.ts P144p30fps16x9,P240p30fps16x9 nv 2
+```
+
 You can follow the development of LPMS and Livepeer @ our [forum](http://forum.livepeer.org)

cmd/transcoding/transcoding.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/livepeer/lpms/ffmpeg"
+)
+
+func validRenditions() []string {
+	valids := make([]string, len(ffmpeg.VideoProfileLookup))
+	for p, _ := range ffmpeg.VideoProfileLookup {
+		valids = append(valids, p)
+	}
+	return valids
+}
+
+func main() {
+	if len(os.Args) <= 3 {
+		panic("Usage: <input file> <output renditions, comma separated> <sw/nv>")
+	}
+	str2accel := func(inp string) (ffmpeg.Acceleration, string) {
+		if inp == "nv" {
+			return ffmpeg.Nvidia, "nv"
+		}
+		return ffmpeg.Software, "sw"
+	}
+	str2profs := func(inp string) []ffmpeg.VideoProfile {
+		profs := []ffmpeg.VideoProfile{}
+		strs := strings.Split(inp, ",")
+		for _, k := range strs {
+			p, ok := ffmpeg.VideoProfileLookup[k]
+			if !ok {
+				panic(fmt.Sprintf("Invalid rendition %s. Valid renditions are:\n%s", k, validRenditions()))
+			}
+			profs = append(profs, p)
+		}
+		return profs
+	}
+	fname := os.Args[1]
+	profiles := str2profs(os.Args[2])
+	accel, lbl := str2accel(os.Args[3])
+
+	profs2opts := func(profs []ffmpeg.VideoProfile) []ffmpeg.TranscodeOptions {
+		opts := []ffmpeg.TranscodeOptions{}
+		for i := range profs {
+			o := ffmpeg.TranscodeOptions{
+				Oname:   fmt.Sprintf("out_%s_%d_out.mkv", lbl, i),
+				Profile: profs[i],
+				Accel:   accel,
+			}
+			opts = append(opts, o)
+		}
+		return opts
+	}
+	options := profs2opts(profiles)
+
+	var dev string
+	if accel == ffmpeg.Nvidia {
+		if len(os.Args) <= 4 {
+			panic("Expected device number")
+		}
+		dev = os.Args[4]
+	}
+
+	ffmpeg.InitFFmpeg()
+
+	fmt.Printf("Setting fname %s encoding %d renditions with %v\n", fname, len(options), lbl)
+	err := ffmpeg.Transcode2(&ffmpeg.TranscodeOptionsIn{
+		Fname:  fname,
+		Accel:  accel,
+		Device: dev,
+	}, options)
+	if err != nil {
+		panic(err)
+	}
+}

test.sh

@@ -42,7 +42,11 @@ go test -logtostderr=true
 t7=$?
 cd ..
 
-if (($t1!=0||$t2!=0||$t3!=0||$t4!=0||$t5!=0||$t6!=0||$t7!=0))
+echo 'Testing example program'
+go run cmd/transcoding/transcoding.go transcoder/test.ts P144p30fps16x9,P240p30fps16x9 sw
+t8=$?
+
+if (($t1!=0||$t2!=0||$t3!=0||$t4!=0||$t5!=0||$t6!=0||$t7!=0||$t8!=0))
 then
     printf "\n\nSome Tests Failed\n\n"
     exit -1