livepeer: add a -hevcDecoding flag

CHANGELOG_PENDING.md

@@ -2,8 +2,12 @@
 
 ## vX.X
 
+This release includes a new `-hevcDecoding` flag for transcoders to configure HEVC decoding. If the flag is omitted, the default behavior on GPUs is unchanged, which is to auto-detect HEVC decoding support at transcoder start-up. Transcoders can disable HEVC decoding on GPUs if there is an issue with HEVC jobs via `-hevcDecoding=false`. CPU transcoders now have HEVC decoding disabled by default since processing HEVC jobs is CPU-heavy, but this can be enabled by setting the `-hevcDecoding` flag.
+
 ### Breaking Changes 🚨🚨
 
+- [#3119](https://github.com/livepeer/go-livepeer/pull/3119) CPU transcoders no longer decode HEVC or VP9 by default
+
 ### Features ⚒
 
 #### General
@@ -14,6 +18,8 @@
 
 #### Transcoder
 
+- [#3119](https://github.com/livepeer/go-livepeer/pull/3119) Add `-hevcDecoding` flag to toggle HEVC decoding
+
 ### Bug Fixes 🐞
 
 #### CLI

cmd/livepeer/livepeer.go

@@ -150,6 +150,7 @@
 	cfg.Nvidia = flag.String("nvidia", *cfg.Nvidia, "Comma-separated list of Nvidia GPU device IDs (or \"all\" for all available devices)")
 	cfg.Netint = flag.String("netint", *cfg.Netint, "Comma-separated list of NetInt device GUIDs (or \"all\" for all available devices)")
 	cfg.TestTranscoder = flag.Bool("testTranscoder", *cfg.TestTranscoder, "Test Nvidia GPU transcoding at startup")
+	cfg.HevcDecoding = flag.Bool("hevcDecoding", *cfg.HevcDecoding, "Enable or disable HEVC decoding")
 
 	// Onchain:
 	cfg.EthAcctAddr = flag.String("ethAcctAddr", *cfg.EthAcctAddr, "Existing Eth account address. For use when multiple ETH accounts exist in the keystore directory")
@@ -237,6 +238,9 @@
 	if !isFlagSet["localVerify"] {
 		res.LocalVerify = nil
 	}
+	if !isFlagSet["hevcDecoding"] {
+		res.HevcDecoding = nil
+	}
 
 	return res
 }

cmd/livepeer/starter/starter.go

@@ -104,6 +104,7 @@
 	CurrentManifest         *bool
 	Nvidia                  *string
 	Netint                  *string
+	HevcDecoding            *bool
 	TestTranscoder          *bool
 	EthAcctAddr             *string
 	EthPassword             *string
@@ -181,6 +182,7 @@
 	defaultCurrentManifest := false
 	defaultNvidia := ""
 	defaultNetint := ""
+	defaultHevcDecoding := false
 	defaultTestTranscoder := true
 
 	// Onchain:
@@ -270,6 +272,7 @@
 		CurrentManifest:      &defaultCurrentManifest,
 		Nvidia:               &defaultNvidia,
 		Netint:               &defaultNetint,
+		HevcDecoding:         &defaultHevcDecoding,
 		TestTranscoder:       &defaultTestTranscoder,
 
 		// Onchain:
@@ -489,10 +492,30 @@
 			// Initialize LB transcoder
 			n.Transcoder = core.NewLoadBalancingTranscoder(devices, tf)
 		} else {
-			// for local software mode, enable all capabilities
-			transcoderCaps = append(core.DefaultCapabilities(), core.OptionalCapabilities()...)
+			// for local software mode, enable most capabilities but remove expensive decoders and non-H264 encoders
+			capsToRemove := []core.Capability{core.Capability_HEVC_Decode, core.Capability_HEVC_Encode, core.Capability_VP8_Encode, core.Capability_VP9_Decode, core.Capability_VP9_Encode}
+			caps := core.OptionalCapabilities()
+			for _, c := range capsToRemove {
+				caps = core.RemoveCapability(caps, c)
+			}
+			transcoderCaps = append(core.DefaultCapabilities(), caps...)
 			n.Transcoder = core.NewLocalTranscoder(*cfg.Datadir)
 		}
+
+		if cfg.HevcDecoding == nil {
+			// do nothing; keep defaults
+		} else if *cfg.HevcDecoding {
+			if !core.HasCapability(transcoderCaps, core.Capability_HEVC_Decode) {
+				if accel != ffmpeg.Software {
+					glog.Info("Enabling HEVC decoding when the hardware does not support it")
+				} else {
+					glog.Info("Enabling HEVC decoding on CPU, may be slow")
+				}
+				transcoderCaps = core.AddCapability(transcoderCaps, core.Capability_HEVC_Decode)
+			}
+		} else if !*cfg.HevcDecoding {
+			transcoderCaps = core.RemoveCapability(transcoderCaps, core.Capability_HEVC_Decode)
+		}
 	}
 
 	if *cfg.Redeemer {

core/capabilities.go

@@ -188,6 +188,20 @@
 	}
 }
 
+func RemoveCapability(haystack []Capability, needle Capability) []Capability {
+	for i, c := range haystack {
+		if c == needle {
+			// TODO use slices.Delete once go-livepeer updates to latest golang
+			return append(haystack[:i], haystack[i+1:]...)
+		}
+	}
+	return haystack
+}
+
+func AddCapability(caps []Capability, newCap Capability) []Capability {
+	return append(caps, newCap)
+}
+
 func NewCapabilityString(caps []Capability) CapabilityString {
 	capStr := CapabilityString{}
 	for _, v := range caps {

core/capabilities_test.go

@@ -489,6 +489,50 @@ func TestCapabilities_LegacyCheck(t *testing.T) {
 	assert.Len(legacyCapabilities, legacyLen) // sanity check no modifications
 }
 
+func TestCapability_RemoveCapability(t *testing.T) {
+	tests := []struct {
+		name     string
+		caps     []Capability
+		toRemove Capability
+		expect   []Capability
+	}{{
+		name:     "empty capability list",
+		caps:     nil,
+		toRemove: Capability_H264,
+		expect:   nil,
+	}, {
+		name:     "capability not in list",
+		caps:     []Capability{Capability_H264, Capability_MPEGTS},
+		toRemove: Capability_MP4,
+		expect:   []Capability{Capability_H264, Capability_MPEGTS},
+	}, {
+		name:     "capability at beginning of list",
+		caps:     []Capability{Capability_H264, Capability_MPEGTS},
+		toRemove: Capability_H264,
+		expect:   []Capability{Capability_MPEGTS},
+	}, {
+		name:     "capability in middle of list",
+		caps:     []Capability{Capability_H264, Capability_MP4, Capability_MPEGTS},
+		toRemove: Capability_MP4,
+		expect:   []Capability{Capability_H264, Capability_MPEGTS},
+	}, {
+		name:     "capability at end of list",
+		caps:     []Capability{Capability_H264, Capability_MPEGTS},
+		toRemove: Capability_MPEGTS,
+		expect:   []Capability{Capability_H264},
+	}, {
+		name:     "last capability",
+		caps:     []Capability{Capability_H264},
+		toRemove: Capability_H264,
+		expect:   []Capability{},
+	}}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expect, RemoveCapability(tt.caps, tt.toRemove))
+		})
+	}
+}
+
 func TestLiveeerVersionCompatibleWith(t *testing.T) {
 	tests := []struct {
 		name                  string