2023-10-13 20:52:26 CST W41D5

examples/decode-video/main.go

@@ -0,0 +1,137 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"syscall"
+
+	ffmpeg "github.com/qrtc/ffmpeg-dev-go"
+)
+
+const (
+	INBUF_SIZE = 4096
+)
+
+func pgmSave(buf *uint8, wrap, xsize, ysize int32, filename string) {
+	f, _ := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0755)
+	fmt.Fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255)
+	for i := int32(0); i < ysize; i++ {
+		f.Write(ffmpeg.SliceWithOffset(buf, i+wrap, xsize))
+	}
+	f.Close()
+}
+
+func decode(decCtx *ffmpeg.AvCodecContext, frame *ffmpeg.AvFrame, pkt *ffmpeg.AvPacket, filename string) {
+	ret := ffmpeg.AvCodecSendPacket(decCtx, pkt)
+	if ret < 0 {
+		fmt.Fprintf(os.Stderr, "Error sending a packet for decoding\n")
+		os.Exit(1)
+	}
+
+	for ret >= 0 {
+		ret = ffmpeg.AvCodecReceiveFrame(decCtx, frame)
+		if ret == ffmpeg.AVERROR(int32(syscall.EAGAIN)) || ret == ffmpeg.AVERROR_EOF {
+			return
+		} else if ret < 0 {
+			fmt.Fprintf(os.Stderr, "Error during decoding\n")
+			os.Exit(1)
+		}
+
+		fmt.Fprintf(os.Stdout, "saving frame %3d\n", decCtx.GetFrameNumber())
+
+		// the picture is allocated by the decoder. no need to free it
+		fname := fmt.Sprintf("%s-%d", filename, decCtx.GetFrameNumber())
+		pgmSave(frame.GetDataIdx(0), frame.GetLinesizeIdx(0), frame.GetWidth(), frame.GetHeight(), fname)
+	}
+}
+
+func main() {
+	if len(os.Args) <= 2 {
+		fmt.Fprintf(os.Stdout, "Usage: %s <input file> <output file>\n", os.Args[0])
+		os.Exit(1)
+	}
+	filename := os.Args[1]
+	outfilename := os.Args[2]
+
+	pkt := ffmpeg.AvPacketAlloc()
+	if pkt == nil {
+		os.Exit(1)
+	}
+
+	codec := ffmpeg.AvCodecFindDecoder(ffmpeg.AV_CODEC_ID_MPEG1VIDEO)
+	if codec == nil {
+		fmt.Fprintf(os.Stderr, "Codec not found\n")
+		os.Exit(1)
+	}
+
+	parser := ffmpeg.AvParserInit(codec.GetID())
+	if parser == nil {
+		fmt.Fprintf(os.Stderr, "Parser not found\n")
+		os.Exit(1)
+	}
+
+	avctx := ffmpeg.AvCodecAllocContext3(codec)
+	if avctx == nil {
+		fmt.Fprintf(os.Stderr, "Could not allocate video codec context\n")
+		os.Exit(1)
+	}
+
+	// For some codecs, such as msmpeg4 and mpeg4, width and height MUST be initialized
+	// there because this information is not available in the bitstream.
+
+	// open it
+	if ffmpeg.AvCodecOpen2(avctx, codec, nil) < 0 {
+		fmt.Fprintf(os.Stderr, "Could not open codec\n")
+		os.Exit(1)
+	}
+
+	inbuf := make([]byte, INBUF_SIZE+ffmpeg.AV_INPUT_BUFFER_PADDING_SIZE)
+
+	f, err := os.OpenFile(filename, os.O_RDONLY, 0666)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Could not open %s\n", filename)
+		os.Exit(1)
+	}
+
+	frame := ffmpeg.AvFrameAlloc()
+	if frame == nil {
+		fmt.Fprintf(os.Stderr, "Could not allocate video frame\n")
+		os.Exit(1)
+	}
+
+	for {
+		// read raw data from the input file
+		dataSize, err := f.Read(inbuf[:INBUF_SIZE])
+		if err == io.EOF || dataSize == 0 {
+			break
+		}
+
+		data := inbuf
+		// use the parser to split the data into frames
+		for dataSize > 0 {
+			ret := ffmpeg.AvParserParse2(parser, avctx, pkt.GetDataAddr(), pkt.GetSizeAddr(),
+				&data[0], int32(dataSize), ffmpeg.AV_NOPTS_VALUE, ffmpeg.AV_NOPTS_VALUE, 0)
+			if ret < 0 {
+				fmt.Fprintf(os.Stderr, "Error while parsing\n")
+				os.Exit(1)
+			}
+			data = data[ret:]
+			dataSize -= int(ret)
+
+			if pkt.GetSize() > 0 {
+				decode(avctx, frame, pkt, outfilename)
+			}
+		}
+	}
+
+	// flush the decoder
+	decode(avctx, frame, nil, outfilename)
+
+	f.Close()
+
+	ffmpeg.AvCodecFreeContext(&avctx)
+	ffmpeg.AvParserClose(parser)
+	ffmpeg.AvFrameFree(&frame)
+	ffmpeg.AvPacketFree(&pkt)
+}