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ffmpeg: Clamp resolutions in filter expression (#417)
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This allows the transcoded resolution to be re-clamped
correctly if the input resolution changes mid-segment.

As a result, we no longer need to do this clamping in golang.

Additionally, make the behavior between GPU and CPU more consistent
by applying nvidia codec limits and clamping CPU transcodes.
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@j0sh
j0sh authored Aug 19, 2024
1 parent 9d6ea5f commit f873529
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Showing 3 changed files with 151 additions and 233 deletions.
129 changes: 41 additions & 88 deletions ffmpeg/ffmpeg.go
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Original file line number Diff line number Diff line change
Expand Up @@ -538,18 +538,6 @@ type CodingSizeLimit struct {
WidthMax, HeightMax int
}

type Size struct {
W, H int
}

func (s *Size) Valid(l *CodingSizeLimit) bool {
if s.W < l.WidthMin || s.W > l.WidthMax || s.H < l.HeightMin || s.H > l.HeightMax {
glog.Warningf("[not valid] profile %dx%d\n", s.W, s.H)
return false
}
return true
}

func clamp(val, min, max int) int {
if val <= min {
return min
Expand All @@ -560,76 +548,12 @@ func clamp(val, min, max int) int {
return val
}

func (l *CodingSizeLimit) Clamp(p *VideoProfile, format MediaFormatInfo) error {
w, h, err := VideoProfileResolution(*p)
if err != nil {
return err
}
if w <= 0 || h <= 0 {
return fmt.Errorf("input resolution invalid; probe found w=%d h=%d", w, h)
}
// detect correct rotation
outputAr := float32(w) / float32(h)
inputAr := float32(format.Width) / float32(format.Height)
if (inputAr > 1.0) != (outputAr > 1.0) {
// comparing landscape to portrait, apply rotate on chosen resolution
w, h = h, w
}
// Adjust to minimal encode dimensions keeping aspect ratio

var adjustedWidth, adjustedHeight Size
adjustedWidth.W = clamp(w, l.WidthMin, l.WidthMax)
adjustedWidth.H = format.ScaledHeight(adjustedWidth.W)
adjustedHeight.H = clamp(h, l.HeightMin, l.HeightMax)
adjustedHeight.W = format.ScaledWidth(adjustedHeight.H)
if adjustedWidth.Valid(l) {
p.Resolution = fmt.Sprintf("%dx%d", adjustedWidth.W, adjustedWidth.H)
return nil
}
if adjustedHeight.Valid(l) {
p.Resolution = fmt.Sprintf("%dx%d", adjustedHeight.W, adjustedHeight.H)
return nil
}
// Improve error message to include calculation context
return fmt.Errorf("profile %dx%d size out of bounds %dx%d-%dx%d input=%dx%d adjusted %dx%d or %dx%d",
w, h, l.WidthMin, l.WidthMin, l.WidthMax, l.HeightMax, format.Width, format.Height, adjustedWidth.W, adjustedWidth.H, adjustedHeight.W, adjustedHeight.H)
}

// 7th Gen NVENC limits:
var nvidiaCodecSizeLimts = map[VideoCodec]CodingSizeLimit{
H264: {146, 50, 4096, 4096},
H265: {132, 40, 8192, 8192},
}

func ensureEncoderLimits(outputs []TranscodeOptions, format MediaFormatInfo) error {
// not using range to be able to make inplace modifications to outputs elements
for i := 0; i < len(outputs); i++ {
if outputs[i].Accel == Nvidia {
limits, haveLimits := nvidiaCodecSizeLimts[outputs[i].Profile.Encoder]
resolutionSpecified := outputs[i].Profile.Resolution != ""
// Sometimes rendition Resolution is not specified. We skip this rendition.
if haveLimits && resolutionSpecified {
err := limits.Clamp(&outputs[i].Profile, format)
if err != nil {
// add more context to returned error
p := outputs[i].Profile
return fmt.Errorf(
"%w; profile index=%d Resolution=%s FPS=%d/%d bps=%s codec=%d input ac=%s vc=%s w=%d h=%d",
err, i,
p.Resolution,
p.Framerate, p.FramerateDen, // given FramerateDen == 0 is corrected to be 1
p.Bitrate,
p.Encoder,
format.Acodec, format.Vcodec,
format.Width, format.Height,
)
}
}
}
}
return nil
}

func isAudioAllDrop(ps []TranscodeOptions) bool {
for _, p := range ps {
if p.AudioEncoder.Name != "drop" {
Expand Down Expand Up @@ -667,8 +591,46 @@ func createCOutputParams(input *TranscodeOptionsIn, ps []TranscodeOptions) ([]C.
return params, finalizer, err
}
}
// preserve aspect ratio along the larger dimension when rescaling
filters := fmt.Sprintf("%s='w=if(gte(iw,ih),%d,-2):h=if(lt(iw,ih),%d,-2)'", scale_filter, w, h)

// use these as common limits even for non-nvidia
limits := nvidiaCodecSizeLimts[param.Encoder]
w = clamp(w, limits.WidthMin, limits.WidthMax)
h = clamp(h, limits.HeightMin, limits.HeightMax)

/*
use the larger dimension requested from the transcode resolution
and proportionally rescale the smaller side of the input down
this does imply transposing the dimensions if necessary
if this causes the smaller side to rescale below the minimum
then set the smaller side to the minimum
and rescale the larger side instead
NB possibility that could also blow past the maximum
but the aspect ratio would have to be super skewed
TODO check for unsupportable aspect ratios in the C
*/

maxD := w
if h > w {
maxD = h
}

wExpr := fmt.Sprintf(`trunc(
if(gte(iw,ih),
if(gte(%d*ih/iw,%d),%d,-2),
if(gte(%d,%d*iw/ih),%d,-2)
)/2)*2`, maxD, limits.HeightMin, maxD, limits.WidthMin, maxD, limits.WidthMin)

hExpr := fmt.Sprintf(`trunc(
if(gt(ih,iw),
if(gte(%d*iw/ih,%d),%d,-2),
if(gte(%d,%d*ih/iw),%d,-2)
)/2)*2`, maxD, limits.WidthMin, maxD, limits.HeightMin, maxD, limits.HeightMin)

filters := fmt.Sprintf("%s='w=%s:h=%s'", scale_filter, wExpr, hExpr)

if interpAlgo != "" {
filters = fmt.Sprintf("%s:interp_algo=%s", filters, interpAlgo)
}
Expand Down Expand Up @@ -912,16 +874,7 @@ func (t *Transcoder) Transcode(input *TranscodeOptionsIn, ps []TranscodeOptions)
if err != nil {
return nil, err
}
videoTrackPresent := format.Vcodec != ""
if status == CodecStatusOk && videoTrackPresent {
// We don't return error in case status != CodecStatusOk because proper error would be returned later in the logic.
// Like 'TranscoderInvalidVideo' or `No such file or directory` would be replaced by error we specify here.
// here we require input size and aspect ratio
err = ensureEncoderLimits(ps, format)
if err != nil {
return nil, err
}
}
// TODO hoist the rest of this into C so we don't have to invoke GetCodecInfo
if !t.started {
// NeedsBypass is state where video is present in container & without any frames
videoMissing := status == CodecStatusNeedsBypass || format.Vcodec == ""
Expand Down
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