/**
The purpose of this file is to scale and change the bitrate of a given file.
Useful links that help understand what is going on:
1. http://dranger.com/ffmpeg/tutorial01.html
**/
func main() {
filename := "sample.mp4"
var (
ctxtFormat *avformat.Context
)
// Register all formats and codecs
avformat.AvRegisterAll()
avfilter.AvfilterRegisterAll()
// Open video file
if avformat.AvformatOpenInput(&ctxtFormat, filename, nil, nil) != 0 {
log.Println("Error: Couldn't open file.")
return
}
// Retrieve stream information
//This function populates pFormatCtx->streams with the proper information.
if ctxtFormat.AvformatFindStreamInfo(nil) < 0 {
log.Println("Error: Couldn't find stream information.")
return
}
//We introduce a handy debugging function to show us what's inside
// Dump information about file onto standard error
ctxtFormat.AvDumpFormat(0, filename, 0)
for i := uint(0); i < ctxtFormat.NbStreams(); i++ {
log.Println(ctxtFormat.Streams(i).Codec().CodecType() == avutil.AVMEDIA_TYPE_VIDEO)
}
}
func main() {
filename := "sample.mp4"
var (
ctxtFormat *avformat.Context
ctxtSource *avcodec.Context
ctxtDest *avcodec.Context
videoCodec *avcodec.Codec
videoFrame *avutil.Frame
videoFrameRGB *avutil.Frame
packet *avcodec.Packet
ctxtSws *swscale.Context
videoStream int
frameFinished int
numBytes int
url string
)
//media_type *avutil.MediaType
// Register all formats and codecs
avformat.AvRegisterAll()
// Open video file
if avformat.AvformatOpenInput(&ctxtFormat, filename, nil, nil) != 0 {
log.Println("Error: Couldn't open file.")
return
}
// Retrieve stream information
if ctxtFormat.AvformatFindStreamInfo(nil) < 0 {
log.Println("Error: Couldn't find stream information.")
return
}
// Dump information about file onto standard error
ctxtFormat.AvDumpFormat(0, url, 0)
// Find the first video stream
videoStream = -1
//ctxtFormat->nb_streams
n := ctxtFormat.NbStreams()
//ctxtFormat->streams[]
s := ctxtFormat.Streams()
//s2 := avformat.StreamsOne(ctxtFormat, 1)
log.Print("Number of Streams:", n)
for i := 0; i < int(n); i++ {
// ctxtFormat->streams[i]->codec->codec_type
log.Println("Stream Number:", i)
//FIX: AvMEDIA_TYPE_VIDEO
if (*avformat.CodecContext)(s.Codec()) != nil {
videoStream = i
break
}
}
if videoStream == -1 {
log.Println("Couldn't find a video stream")
return
}
codec := s.Codec()
// Get a pointer to the codec context for the video stream
//ctxtSource = ctxtFormat.streams[videoStream].codec
ctxtSource = (*avcodec.Context)(unsafe.Pointer(&codec))
log.Println("Bit Rate:", ctxtSource.BitRate())
log.Println("Channels:", ctxtSource.Channels())
log.Println("Coded_height:", ctxtSource.CodedHeight())
log.Println("Coded_width:", ctxtSource.CodedWidth())
log.Println("Coder_type:", ctxtSource.CoderType())
log.Println("Height:", ctxtSource.Height())
log.Println("Profile:", ctxtSource.Profile())
log.Println("Width:", ctxtSource.Width())
log.Println("Codec ID:", ctxtSource.CodecId())
//C.enum_AVCodecID
codec_id := ctxtSource.CodecId()
// Find the decoder for the video stream
videoCodec = avcodec.AvcodecFindDecoder(codec_id)
if videoCodec == nil {
log.Println("Error: Unsupported codec!")
return // Codec not found
}
// Copy context
ctxtDest = videoCodec.AvcodecAllocContext3()
if ctxtDest.AvcodecCopyContext(ctxtSource) != 0 {
log.Println("Error: Couldn't copy codec context")
return // Error copying codec context
}
// Open codec
if ctxtDest.AvcodecOpen2(videoCodec, nil) < 0 {
return // Could not open codec
}
// Allocate video frame
videoFrame = avutil.AvFrameAlloc()
// Allocate an Frame structure
if videoFrameRGB = avutil.AvFrameAlloc(); videoFrameRGB == nil {
return
}
//##TODO
var a swscale.PixelFormat
var b int
//avcodec.PixelFormat
//avcodec.PIX_FMT_RGB24
//avcodec.SWS_BILINEAR
w := ctxtDest.Width()
h := ctxtDest.Height()
pix_fmt := ctxtDest.PixFmt()
// Determine required buffer size and allocate buffer
numBytes = avcodec.AvpictureGetSize((avcodec.PixelFormat)(a), w, h)
buffer := avutil.AvMalloc(uintptr(numBytes))
// Assign appropriate parts of buffer to image planes in videoFrameRGB
// Note that videoFrameRGB is an Frame, but Frame is a superset
// of Picture
avp := (*avcodec.Picture)(unsafe.Pointer(videoFrameRGB))
avp.AvpictureFill((*uint8)(buffer), (avcodec.PixelFormat)(a), w, h)
// initialize SWS context for software scaling
ctxtSws = swscale.SwsGetcontext(w,
h,
(swscale.PixelFormat)(pix_fmt),
w,
h,
a,
b,
nil,
nil,
nil,
)
// Read frames and save first five frames to disk
i := 0
for ctxtFormat.AvReadFrame(packet) >= 0 {
// Is this a packet from the video stream?
s := packet.StreamIndex()
if s == videoStream {
// Decode video frame
ctxtDest.AvcodecDecodeVideo2((*avcodec.Frame)(unsafe.Pointer(videoFrame)), &frameFinished, packet)
// Did we get a video frame?
if frameFinished > 0 {
// Convert the image from its native format to RGB
d := avutil.Data(videoFrame)
l := avutil.Linesize(videoFrame)
dr := avutil.Data(videoFrameRGB)
lr := avutil.Linesize(videoFrameRGB)
swscale.SwsScale(ctxtSws,
d,
l,
0,
h,
dr,
lr,
)
// Save the frame to disk
if i <= 5 {
saveFrame(videoFrameRGB, w, h, i)
}
i++
}
}
// Free the packet that was allocated by av_read_frame
packet.AvFreePacket()
}
// Free the RGB image
avutil.AvFree(buffer)
avutil.AvFrameFree(videoFrameRGB)
// Free the YUV frame
avutil.AvFrameFree(videoFrame)
// Close the codecs
ctxtDest.AvcodecClose()
ctxtSource.AvcodecClose()
// Close the video file
ctxtFormat.AvformatCloseInput()
}