i am using stagefright videoencoder to encode video in android 4.4;
sp<AMessage> format = new AMessage;
format->setInt32("width", 1080);
format->setInt32("height", 1920);
format->setString("mime", "video/avc");
format->setInt32("color-format", OMX_COLOR_FormatYUV420Planar);
format->setInt32("bitrate", 1000000);
format->setFloat("frame-rate", 25);
format->setInt32("i-frame-interval", 5);
sp<MediaCodec> videoEncoder = MediaCodec::CreateByType(looper, "video/avc", true);
videoEncoder->configure(format, NULL, NULL,MediaCodec::CONFIGURE_FLAG_ENCODE);
videoEncoder->start();
but when i called:
status_t err = gSpVideoEncoder->dequeueOutputBuffer(&bufIndex, &offset, &size, &ptsUsec, &flags, kTimeout);
i got:
err === INFO_FORMAT_CHANGED
next step, I called:
sp<AMessage> newFormat;
videoEncoder->getOutputFormat(&newFormat);
uint32_t width = 0, height = 0;
newFormat->findInt32("width", (int32_t *)(&width));
newFormat->findInt32("height", (int32_t *)(&height));
fprintf(stderr, "new width: %d, height: %d\n", width, height)
I got result:
new width: 1088, height: 1920
I am confused(not 1080x1920), whether i should provide new input frame(1088x1920) to videoEncoder?
Video coding requires the frame dimensions to be aligned to multiples of 16 i.e. macroblock dimensions. HD resolution i.e. 1920 x 1080 is a special case as 1080 is not a multiple of 16. The underlying encoder expects the client to provide an aligned boundary.
In this case, you could provide the data windowed as below. For Luma, you will have to align to a multiple of 16 and for Chroma, you will have to align to a multiple of 8. The remaining pixels could be prefilled with zeroes.
Please note: If the encoder is capable of handling 1920 x 1080 as an encoding resolution, the output should be fine. If the encoder encodes with 1920 x 1088, you will observe a green band at the bottom of the picture in the generated bitstream due to the zero padding.
---------------------------------------------
| |
| |
| |
| Luma |
| 1920 x 1080 |
| filled into |
| a buffer of |
| 1920 x 1088 |
| |
| Last 8 lines could |
| be filled with zeroes |
| |
---------------------------------------------
-----------------------
| Cb |
| 960 x 540 |
| filled into |
| a buffer of |
| 960 x 544 |
| |
-----------------------
-----------------------
| Cr |
| 960 x 540 |
| filled into |
| a buffer of |
| 960 x 544 |
| |
-----------------------