The clips on http://hoverstat.es/ are the best examples of what I am after.
The spec are roughly:
Format/Codec: mp4/h.264
Dimension: 1280x720
Audio: disabled
File size: 1.5Mb for a 15 second clip (0.1Mb/s)
Bitrate: ~750
Quality: Near as sharp and crisp as screenshots; minimum visible loss/blur
I am using Quicktime to do screen recordings. Outputting file from MOV to MP4 with Handbrake (http://handbrake.fr/) on Mac. Managed to decrease file size significantly by setting bitrate to ~750 but the video quality is horrible. No where near clear and readable, not to mention crisp and sharp.
Any help is appreciated!
Have a try with AppGeeker, it compresses videos into a small file with a little loss of file quality.
http://www.appgeeker.com/how-to/convert-mp4-to-mov-mac.html
Make sure set the preferences to "High Quality" in its settings panel.
Related
I have tried converting the audio file prior to importing into unity to both 44.1k and 48k sample rates and they sounds identical when played back in unity (slowed down and pitched down). I have tried this with a .wav file and a .aif at both sample rates mentioned above and it sounds the same. Any ideas why this is happening?
When I tried to upload a preview video followed by apple's guide, itunesconenct popup an error:
Any one knows how to solve this? Thanks,
Apple's Guide:
https://developer.apple.com/app-store/app-previews/
Movies in App Reviews are to have max frame rate of 30 fps. Therefore, you have to find ways to reduce your video frame rate. I reduced mine to 24 fps and got accepted by App Store. There are options as discussed below.
A. Using Terminal:
i) install ffmpeg program if you don't have:
brew install ffmpeg --with-chromaprint --with-fdk-aac --with-libass --with-librsvg --with-libsoxr --with-libssh --with-tesseract --with-libvidstab --with-opencore-amr --with-openh264 --with-openjpeg --with-openssl --with-rtmpdump --with-rubberband --with-sdl2 --with-snappy --with-tools --with-webp --with-x265 --with-xz --with-zeromq --with-zimg
ii) run ffmpeg to force changing frame rate to, 24 fps, for example.
ffmpeg -i input.mp4 -r 24 output.mp4
B. Using a graphical program such LumaFusion. You can buy LumaFusion and install on an iPhone/iPad, and change frame rate upon saving the video.
C. I tried to change the frame rate on iMovie, version 10.1.9, (on the Mac High Sierra 10.13.6), but there is straight forward way to change frame rate.
Please check the official App Preview Properties: https://developer.apple.com/library/content/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/Properties.html#//apple_ref/doc/uid/TP40011225-CH26-SW10
Specifically, the Max Frame Rate is 30 fps
As you didn't mention, how you took the App Preview, I would recommend a video editing tool like iMovie, Adobe After Effects or Final Cut Pro to reduce the frame rate to the 30 fps limit.
I use DaVinci Resolve to create previews for the App Store.
There is a free download here. https://www.blackmagicdesign.com/products/davinciresolve/.
Set the project to the proper resolution (e.g. 866x1920 or 1080x1920).
Import the clip to the timeline
Right click and set the clips properties to 30FPS.
Select File -> Media Management
Then Transcode option
Set the wrapper to MP4 and the CODEC to H.264
Your clip will be exported in the proper format.
I’m working on a Matlab application that uses a VLC class to control a VLC-instance. One of the features is to set the VLC player to fullscreen. This feature works perfectly fine.
The VLC player is downloaded from Matlab’s File Exchange: https://se.mathworks.com/matlabcentral/fileexchange/56215-vlc (Thanks a lot Léa Strobino)
However, one particular clip insists on resizing the player to a smaller size.
I have done some research and it turns out that this is a common problem in some VLC versions.
Normal workarounds are to uncheck the “adapt interface to video size” (something like that) and to check the “Fullscreen” box.
This ought to make the player open in fullscreen and not resize the screen to video size. The video still resizes the player to a smaller size.
All the specs of the clips are the same: Same file extension (.vob), formats and were made the same way (I did some video trimming and such using ffmpeg – but the same way every time).
I have noticed one difference and that is that this particular video has a lower Data and bitrate (~1000-1500kbps) where as the others are higher (<4000kbps). Also when showing the properties of the clip the frame height and width are blank as opposed to the others that have specific values.
This should however not have an effect of the fullscreen command from Matlab called after loading the video into the playlist. The command has no effect on this video, but does on all other.
It is possible to set the player to fullscreen manually by clicking the window, so it is not caused by some restriction in the video not allowing it to fullscreen.
Why does the video refuse to go in to fullscreen?
Hope somebody is able to help.
Okay so I seem to have solved the problem now. Without being completely sure why - the problem was in the lowered data/framerate.
I tried to add -crf 18 when converting my .mp4 to a .vob file:
ffmpeg -i input.mp4 -vcodec copy -acodec ac3 -crf 18 output.vob
The -crf stands for Constant Rate Factor and is a way to ensure a specific Data rate. The values goes from 0-51 and 18 seems to be the lowest 'sane' value (highest data rate). A good explanation can be found here: https://superuser.com/questions/677576/what-is-crf-used-for-in-ffmpeg
With this higher data rate the video opens up in fullscreen everytime :=)
I am decoding a H264 stream using FFmpeg on the iPhone. I know the H264 stream is valid and the SPS/PPS are correct as VLC, Quicktime, Flash all decode the stream properly. The issue I am having on the iPhone is best shown by this picture.
It is as if the motion vectors are being drawn. This picture was snapped while there was a lot of motion in the image. If the scene is static then there are dots in the corners. This always occurs with predictive frames. The blocky colors are also an issue.
I have tried various build settings for FFmpeg such as turning off optimizations, asm, neon, and many other combinations. Nothing seems to alter the behavior of the decoder. I have also tried the Works with HTML, Love and Peace releases, and also the latest GIT sources. Is there maybe a setting I am missing, or maybe I have inadvertently enabled some debug setting in the decoder.
Edit
I am using sws_scale to convert the image to RGBA. I have tried various different pixel formats with the same results.
sws_scale(convertCtx, (const uint8_t**)srcFrame->data, srcFrame->linesize, 0, codecCtx->height, dstFrame->data, dstFrame->linesize);
I am using PIX_FMT_YUV420P as the source format when setting up my codec context.
What you're looking at is ffmpeg's motion vector visualization. Make sure that none of the following debug flags are set:
avctx->debug & FF_DEBUG_VIS_QP
avctx->debug & FF_DEBUG_VIS_MB_TYPE
avctx->debug_mv
Also, keep in mind that decoding H264 video using the CPU will be MUCH slower and less power-efficient on iOS than using the hardware decoder.
I'm trying to do some image processing on iPhone.
I'm using http://developer.apple.com/library/ios/#qa/qa2010/qa1702.html to capture the camera frames.
I saw that I can set AVCaptureVideoDataOutput image format using setVideoSettings, but is it possible to get the images in lower resolution?
If not, is the an efficient way to downscale the resulted image?
Thanks,
Asaf.
This is how we can get a lower resolution output so we get a higher FPS when manipulating the image:
// sessionPreset governs the quality of the capture. we don't need high-resolution images,
// so we'll set the session preset to low quality.
self.captureSession.sessionPreset = AVCaptureSessionPresetLow;
Asaf Pinhassi.