public IplImage grab() throws Exception {
if (pFormatCtx == null || pFormatCtx.isNull()) {
throw new Exception("Could not grab: No AVFormatContext. (Has start() been called?)");
}
boolean done = false;
long pts = 0;
while (!done) {
if (av_read_frame(pFormatCtx, packet) < 0) {
// throw new Exception("Could not read frame");
return null; // end of file?
}
// Is this a packet from the video stream?
if (packet.stream_index() == videoStream) {
// Decode video frame
int len = avcodec_decode_video2(pCodecCtx, pFrame, frameFinished, packet);
LongPointer opaque = new LongPointer(pFrame.opaque());
if (packet.dts() != AV_NOPTS_VALUE) {
pts = packet.dts();
} else if (!opaque.isNull() && opaque.get() != AV_NOPTS_VALUE) {
pts = opaque.get();
} else {
pts = 0;
}
AVRational time_base = pStream.time_base();
pts = 1000 * pts * time_base.num() / time_base.den();
// Did we get a video frame?
if (len > 0 && frameFinished[0] != 0) {
switch (colorMode) {
case BGR:
case GRAY:
// Deinterlace Picture
if (deinterlace) {
avpicture_deinterlace(
pFrame, pFrame, pCodecCtx.pix_fmt(), pCodecCtx.width(), pCodecCtx.height());
}
// Convert the image from its native format to RGB
sws_scale(
img_convert_ctx,
new PointerPointer(pFrame),
pFrame.linesize(),
0,
pCodecCtx.height(),
new PointerPointer(pFrameRGB),
pFrameRGB.linesize());
return_image.imageData(buffer);
return_image.widthStep(pFrameRGB.linesize(0));
break;
case RAW:
assert (pCodecCtx.width() == return_image.width()
&& pCodecCtx.height() == return_image.height());
return_image.imageData(pFrame.data(0));
return_image.widthStep(pFrame.linesize(0));
break;
default:
assert (false);
}
return_image.imageSize(return_image.height() * return_image.widthStep());
done = true;
}
}
// Free the packet that was allocated by av_read_frame
av_free_packet(packet);
}
return_image.timestamp = pts;
return return_image;
}
public void start() throws Exception {
// Open video file
AVInputFormat f = null;
if (format != null && format.length() > 0) {
f = av_find_input_format(format);
if (f == null) {
throw new Exception("Could not find input format \"" + format + "\".");
}
}
AVFormatParameters fp = null;
if (frameRate > 0 || bpp > 0 || imageWidth > 0 || imageHeight > 0) {
fp = new AVFormatParameters();
fp.time_base(av_d2q(1 / frameRate, FFmpegFrameRecorder.DEFAULT_FRAME_RATE_BASE));
fp.sample_rate(bpp);
fp.channels(colorMode == ColorMode.BGR ? 3 : 1);
fp.width(imageWidth);
fp.height(imageHeight);
}
if (av_open_input_file(pFormatCtx, filename, f, 0, fp) != 0) {
throw new Exception("Could not open file \"" + filename + "\".");
}
// Retrieve stream information
if (av_find_stream_info(pFormatCtx) < 0) {
throw new Exception("Could not find stream information.");
}
// Dump information about file onto standard error
dump_format(pFormatCtx, 0, filename, 0);
// Find the first video stream
videoStream = -1;
int nb_streams = pFormatCtx.nb_streams();
for (int i = 0; i < nb_streams; i++) {
pStream = pFormatCtx.streams(i);
// Get a pointer to the codec context for the video stream
pCodecCtx = pStream.codec();
if (pCodecCtx.codec_type() == CODEC_TYPE_VIDEO) {
videoStream = i;
break;
}
}
if (videoStream == -1) {
throw new Exception("Did not find a video stream.");
}
// Find the decoder for the video stream
pCodec = avcodec_find_decoder(pCodecCtx.codec_id());
if (pCodec == null) {
throw new Exception("Unsupported codec or codec not found: " + pCodecCtx.codec_id() + ".");
}
// Open codec
if (avcodec_open(pCodecCtx, pCodec) < 0) {
throw new Exception("Could not open codec.");
}
// Allocate video frame
pFrame = avcodec_alloc_frame();
// Allocate an AVFrame structure
pFrameRGB = avcodec_alloc_frame();
if (pFrameRGB == null) {
throw new Exception("Could not allocate frame.");
}
int width = getImageWidth() > 0 ? getImageWidth() : pCodecCtx.width();
int height = getImageHeight() > 0 ? getImageHeight() : pCodecCtx.height();
switch (colorMode) {
case BGR:
// Determine required buffer size and allocate buffer
numBytes = avpicture_get_size(PIX_FMT_BGR24, width, height);
buffer = new BytePointer(av_malloc(numBytes));
// Assign appropriate parts of buffer to image planes in pFrameRGB
// Note that pFrameRGB is an AVFrame, but AVFrame is a superset
// of AVPicture
avpicture_fill(pFrameRGB, buffer, PIX_FMT_BGR24, width, height);
// Convert the image into BGR format that OpenCV uses
img_convert_ctx =
sws_getContext(
pCodecCtx.width(),
pCodecCtx.height(),
pCodecCtx.pix_fmt(),
width,
height,
PIX_FMT_BGR24,
SWS_BILINEAR,
null,
null,
null);
if (img_convert_ctx == null) {
throw new Exception("Cannot initialize the conversion context.");
}
return_image = IplImage.createHeader(width, height, IPL_DEPTH_8U, 3);
break;
case GRAY:
numBytes = avpicture_get_size(PIX_FMT_GRAY8, width, height);
buffer = new BytePointer(av_malloc(numBytes));
avpicture_fill(pFrameRGB, buffer, PIX_FMT_GRAY8, width, height);
// Convert the image into GRAY format that OpenCV uses
img_convert_ctx =
sws_getContext(
pCodecCtx.width(),
pCodecCtx.height(),
pCodecCtx.pix_fmt(),
width,
height,
PIX_FMT_GRAY8,
SWS_BILINEAR,
null,
null,
null);
if (img_convert_ctx == null) {
throw new Exception("Cannot initialize the conversion context.");
}
return_image = IplImage.createHeader(width, height, IPL_DEPTH_8U, 1);
break;
case RAW:
numBytes = 0;
buffer = null;
img_convert_ctx = null;
return_image =
IplImage.createHeader(pCodecCtx.width(), pCodecCtx.height(), IPL_DEPTH_8U, 1);
break;
default:
assert (false);
}
}