Fixed timebases

Author: djthorpe

cmd/examples/encode/context.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"context"
+	"os"
+	"os/signal"
+)
+
+///////////////////////////////////////////////////////////////////////////////
+// PUBLIC METHODS
+
+// ContextForSignal returns a context object which is cancelled when a signal
+// is received. It returns nil if no signal parameter is provided
+func ContextForSignal(signals ...os.Signal) context.Context {
+	if len(signals) == 0 {
+		return nil
+	}
+
+	ch := make(chan os.Signal, 1)
+	ctx, cancel := context.WithCancel(context.Background())
+
+	// Send message on channel when signal received
+	signal.Notify(ch, signals...)
+
+	// When any signal received, call cancel
+	go func() {
+		<-ch
+		cancel()
+	}()
+
+	// Return success
+	return ctx
+}

cmd/examples/encode/main.go

@@ -1,10 +1,13 @@
 package main
 
 import (
+	"context"
+	"errors"
 	"fmt"
 	"io"
 	"log"
 	"os"
+	"syscall"
 
 	// Packages
 	ffmpeg "github.com/mutablelogic/go-media/pkg/ffmpeg"
@@ -13,9 +16,14 @@ import (
 
 // This example encodes an audio an video stream to a file
 func main() {
+	// Check we have a filename
+	if len(os.Args) != 2 {
+		log.Fatal("Usage: encode filename")
+	}
+
 	// Create a new file with an audio and video stream
 	file, err := ffmpeg.Create(os.Args[1],
-		ffmpeg.OptStream(1, ffmpeg.VideoPar("yuv420p", "1280x720", 30)),
+		ffmpeg.OptStream(1, ffmpeg.VideoPar("yuv420p", "1280x720", 25, ffmpeg.NewMetadata("crf", 2))),
 		ffmpeg.OptStream(2, ffmpeg.AudioPar("fltp", "mono", 22050)),
 	)
 	if err != nil {
@@ -39,10 +47,13 @@ func main() {
 	}
 	defer audio.Close()
 
+	// Bail out when we receive a signal
+	ctx := ContextForSignal(os.Interrupt, syscall.SIGQUIT)
+
 	// Write 90 seconds, passing video and audio frames to the encoder
 	// and returning io.EOF when the duration is reached
 	duration := float64(90)
-	err = file.Encode(func(stream int) (*ffmpeg.Frame, error) {
+	err = file.Encode(ctx, func(stream int) (*ffmpeg.Frame, error) {
 		var frame *ffmpeg.Frame
 		switch stream {
 		case 1:
@@ -51,12 +62,12 @@ func main() {
 			frame = audio.Frame()
 		}
 		if frame != nil && frame.Ts() < duration {
-			fmt.Print(".")
+			fmt.Println(stream, frame.Ts())
 			return frame, nil
 		}
 		return nil, io.EOF
 	}, nil)
-	if err != nil {
+	if err != nil && !errors.Is(err, context.Canceled) {
 		log.Fatal(err)
 	}
 	fmt.Print("\n")

pkg/ffmpeg/encoder.go

@@ -72,7 +72,7 @@ func NewEncoder(ctx *ff.AVFormatContext, stream int, par *Par) (*Encoder, error)
 	}
 
 	// Create the stream
-	if streamctx := ff.AVFormat_new_stream(ctx, nil); streamctx == nil {
+	if streamctx := ff.AVFormat_new_stream(ctx, codec); streamctx == nil {
 		ff.AVCodec_free_context(encoder.ctx)
 		return nil, ErrInternalAppError.With("could not allocate stream")
 	} else {
@@ -86,20 +86,40 @@ func NewEncoder(ctx *ff.AVFormatContext, stream int, par *Par) (*Encoder, error)
 		encoder.ctx.SetFlags(encoder.ctx.Flags() | ff.AV_CODEC_FLAG_GLOBAL_HEADER)
 	}
 
+	// Get the options
+	opts := par.newOpts()
+	if opts == nil {
+		ff.AVCodec_free_context(encoder.ctx)
+		return nil, ErrInternalAppError.With("could not allocate options dictionary")
+	}
+	defer ff.AVUtil_dict_free(opts)
+
 	// Open it
-	if err := ff.AVCodec_open(encoder.ctx, codec, nil); err != nil {
+	if err := ff.AVCodec_open(encoder.ctx, codec, opts); err != nil {
 		ff.AVCodec_free_context(encoder.ctx)
 		return nil, ErrInternalAppError.Withf("codec_open: %v", err)
 	}
 
+	// If there are any non-consumed options, then error
+	var result error
+	for _, key := range ff.AVUtil_dict_keys(opts) {
+		result = errors.Join(result, ErrBadParameter.Withf("Stream %d: invalid codec option %q", stream, key))
+	}
+	if result != nil {
+		ff.AVCodec_free_context(encoder.ctx)
+		return nil, result
+	}
+
 	// Copy parameters to stream
 	if err := ff.AVCodec_parameters_from_context(encoder.stream.CodecPar(), encoder.ctx); err != nil {
 		ff.AVCodec_free_context(encoder.ctx)
 		return nil, err
-	} else {
-		encoder.stream.SetTimeBase(par.timebase)
 	}
 
+	// Hint what timebase we want to encode at. This will change when writing the
+	// headers for the encoding process
+	encoder.stream.SetTimeBase(par.timebase)
+
 	// Create a packet
 	packet := ff.AVCodec_packet_alloc()
 	if packet == nil {
@@ -167,7 +187,7 @@ func (e *Encoder) Encode(frame *Frame, fn EncoderPacketFn) error {
 // Return the codec parameters
 func (e *Encoder) Par() *Par {
 	par := new(Par)
-	par.timebase = e.stream.TimeBase()
+	par.timebase = e.ctx.TimeBase()
 	if err := ff.AVCodec_parameters_from_context(&par.AVCodecParameters, e.ctx); err != nil {
 		return nil
 	} else {
@@ -180,9 +200,9 @@ func (e *Encoder) nextPts(frame *Frame) int64 {
 	next_pts := int64(0)
 	switch e.ctx.Codec().Type() {
 	case ff.AVMEDIA_TYPE_AUDIO:
-		next_pts = ff.AVUtil_rational_rescale_q(int64(frame.NumSamples()), ff.AVUtil_rational(1, frame.SampleRate()), e.stream.TimeBase())
+		next_pts = ff.AVUtil_rational_rescale_q(int64(frame.NumSamples()), frame.TimeBase(), e.stream.TimeBase())
 	case ff.AVMEDIA_TYPE_VIDEO:
-		next_pts = ff.AVUtil_rational_rescale_q(1, ff.AVUtil_rational_invert(e.ctx.Framerate()), e.stream.TimeBase())
+		next_pts = ff.AVUtil_rational_rescale_q(1, frame.TimeBase(), e.stream.TimeBase())
 	default:
 		// Dunno what to do with subtitle and data streams yet
 		fmt.Println("TODO: next_pts for subtitle and data streams")

pkg/ffmpeg/par.go

@@ -18,20 +18,25 @@ import (
 
 type Par struct {
 	ff.AVCodecParameters
+	opts     []media.Metadata
 	timebase ff.AVRational
 }
 
 type jsonPar struct {
-	Par      ff.AVCodecParameters `json:"parameters"`
-	Timebase ff.AVRational        `json:"timebase"`
+	ff.AVCodecParameters
+	Timebase ff.AVRational    `json:"timebase"`
+	Opts     []media.Metadata `json:"options"`
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 // LIFECYCLE
 
-func NewAudioPar(samplefmt string, channellayout string, samplerate int) (*Par, error) {
+// Create new audio parameters with sample format, channel layout and sample rate
+// plus any additional options which is used for creating a stream
+func NewAudioPar(samplefmt string, channellayout string, samplerate int, opts ...media.Metadata) (*Par, error) {
 	par := new(Par)
 	par.SetCodecType(ff.AVMEDIA_TYPE_AUDIO)
+	par.opts = opts
 
 	// Sample Format
 	if samplefmt_ := ff.AVUtil_get_sample_fmt(samplefmt); samplefmt_ == ff.AV_SAMPLE_FMT_NONE {
@@ -59,9 +64,12 @@ func NewAudioPar(samplefmt string, channellayout string, samplerate int) (*Par,
 	return par, nil
 }
 
-func NewVideoPar(pixfmt string, size string, framerate float64) (*Par, error) {
+// Create new video parameters with pixel format, frame size, framerate
+// plus any additional options which is used for creating a stream
+func NewVideoPar(pixfmt string, size string, framerate float64, opts ...media.Metadata) (*Par, error) {
 	par := new(Par)
 	par.SetCodecType(ff.AVMEDIA_TYPE_VIDEO)
+	par.opts = opts
 
 	// Pixel Format
 	if pixfmt_ := ff.AVUtil_get_pix_fmt(pixfmt); pixfmt_ == ff.AV_PIX_FMT_NONE {
@@ -88,37 +96,22 @@ func NewVideoPar(pixfmt string, size string, framerate float64) (*Par, error) {
 	// Set default sample aspect ratio
 	par.SetSampleAspectRatio(ff.AVUtil_rational(1, 1))
 
-	// TODO: Set profile, codec and bitrate and any other parameters
-
-	/* TODO
-	c->gop_size      = 12; // emit one intra frame every twelve frames at most
-	c->pix_fmt       = STREAM_PIX_FMT;
-	if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
-		// just for testing, we also add B-frames
-		c->max_b_frames = 2;
-	}
-	if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
-		// Needed to avoid using macroblocks in which some coeffs overflow.
-		// This does not happen with normal video, it just happens here as
-		// the motion of the chroma plane does not match the luma plane.
-		c->mb_decision = 2;
-	}
-	*/
-
 	// Return success
 	return par, nil
 }
 
-func AudioPar(samplefmt string, channellayout string, samplerate int) *Par {
-	if par, err := NewAudioPar(samplefmt, channellayout, samplerate); err != nil {
+// Create audio parameters. If there is an error, then this function will panic
+func AudioPar(samplefmt string, channellayout string, samplerate int, opts ...media.Metadata) *Par {
+	if par, err := NewAudioPar(samplefmt, channellayout, samplerate, opts...); err != nil {
 		panic(err)
 	} else {
 		return par
 	}
 }
 
-func VideoPar(pixfmt string, size string, framerate float64) *Par {
-	if par, err := NewVideoPar(pixfmt, size, framerate); err != nil {
+// Create video parameters. If there is an error, then this function will panic
+func VideoPar(pixfmt string, size string, framerate float64, opts ...media.Metadata) *Par {
+	if par, err := NewVideoPar(pixfmt, size, framerate, opts...); err != nil {
 		panic(err)
 	} else {
 		return par
@@ -130,8 +123,9 @@ func VideoPar(pixfmt string, size string, framerate float64) *Par {
 
 func (ctx *Par) MarshalJSON() ([]byte, error) {
 	return json.Marshal(jsonPar{
-		Par:      ctx.AVCodecParameters,
-		Timebase: ctx.timebase,
+		AVCodecParameters: ctx.AVCodecParameters,
+		Timebase:          ctx.timebase,
+		Opts:              ctx.opts,
 	})
 }
 
@@ -196,6 +190,19 @@ func (ctx *Par) CopyToCodecContext(codec *ff.AVCodecContext) error {
 ///////////////////////////////////////////////////////////////////////////////
 // PRIVATE METHODS
 
+// Return options as a dictionary, which needs to be freed after use
+// by the caller method
+func (ctx *Par) newOpts() *ff.AVDictionary {
+	dict := ff.AVUtil_dict_alloc()
+	for _, opt := range ctx.opts {
+		if err := ff.AVUtil_dict_set(dict, opt.Key(), opt.Value(), ff.AV_DICT_APPEND); err != nil {
+			ff.AVUtil_dict_free(dict)
+			return nil
+		}
+	}
+	return dict
+}
+
 func (ctx *Par) copyAudioCodec(codec *ff.AVCodecContext) error {
 	codec.SetSampleFormat(ctx.SampleFormat())
 	codec.SetSampleRate(ctx.Samplerate())