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• How can I capture low resolution video on Android reliably across a range of devices ?

  8 décembre 2017, par MisterMat

  Hello Android video experts :)

  I am developing an Android application which allows the user to capture video and upload it to a remote server (it’s more involved than that but the rest of the app is not important). Because of the upload requirement, it is important that the video is of a reasonable size, so not super high resolution. Let’s say a max of 680x480 or 10Mb/minute. This is no problem on Apple devices.

  I have had what can only be described as a complete nightmare trying to capture video at a reasonably low bitrate reliably across a range of Android devices.

  As I understand it there are two ways of capturing video on Android :

  1) Using the Media Recorder/Camera API

  2) Using an Intent to open the cameras video capture application

  Option 1) gives the most flexibility and allows us to easily change the capture resolution. However the Android Camera API is NOT reliable across a range of devices, and I have very good information (including from someone who liaised with Google on this issue) that if you capture video using this API then it will crash on a good 50% of the devices out there. There is a reason that Zoom Camera FX uses an Intent for video capture. Zoom Camera (different app) seems to use Media Recorder, but has lots of bad reviews for video crashing or not working.

  Option 2) works well across a range of devices, as it uses the in built application on the device. The trouble is you have no control whatsoever on the resolution, there is a quality hint on the Intent but the camera app will normally ignore this. My Samsung Galaxy S3 records video by default at about 2Mb/s. This is way too high resolution. The built in application can of course change the resolution, but this relies on action by the user which is difficult to control.

  I understand that I could use a library such as ffmpeg to change the resolution of the video after capture. However this requires me to compile the library for Android, and also I have been informed that in order to legally use the decode/encode codecs on the device you have to pay license fees that amount to about $1 per copy of the app. Since this app will be free to use, this is not an option.

  So that’s where I’m at. I’ve searched long and high for answers, but I can’t figure out how to capture low resolution video reliably using Android.

  Any help very much appreciated !

  Matthew

• lavc/vp8 : Support resolution changes in the VP8 decoder hwaccel

  30 novembre 2017, par Jun Zhao

  lavc/vp8 : Support resolution changes in the VP8 decoder hwaccel
  Use the following command to reproduce this issue :
  
  make fate-vp8-size-change HWACCEL="vaapi -vaapi_device \
  
  /dev/dri/renderD128 -hwaccel_output_format yuv420p"
  
  SAMPLES=../fate-suite/.
  At the same time, reconstruct the public logic as a function.
  Signed-off-by : Yun Zhou <yunx.z.zhou@intel.com>
  
  Signed-off-by : Jun Zhao <jun.zhao@intel.com>
  
  Signed-off-by : Mark Thompson <sw@jkqxz.net>
  

  • [DH] libavcodec/vp8.c

• MP4Box Resolution unmatched between representation

  30 janvier 2018, par Massimo Vantaggio

  for one of the last stability tests i try with two representation instead the only one of before to get the adaptive bitrate streaming .
  Below my encoding command :

  ffmpeg -y -i $name -i logo.png -c:a aac -b:a 256k -ar 48000 -ac 2 -async 1 -c:v libx264 -x264opts keyint=$GOP:min-keyint=$GOP:no-scenecut -bf 0 -r $FPSC -b:v 1060k -maxrate 1060k -bufsize 530k -profile:v main -t $FDUR -filter_complex "[0:v][1:v]overlay=main_w-overlay_w-10:10,scale=-1:478" format480.mp4
  
  
  
  ffmpeg -y -i $name -i logo.png -c:a aac -b:a 384k -ar 48000 -ac 2 -async 1 -c:v libx264 -x264opts keyint=$GOP:min-keyint=$GOP:no-scenecut -bf 0 -r $FPSC -b:v 2400k -maxrate 2400k -bufsize 1200k -profile:v main -t $FDUR -filter_complex "[0:v][1:v]overlay=main_w-overlay_w-10:10,scale=-1:1080" format1080.mp4

  If for the first rapresentation i use 480p ffmpeg give me this error :

  width not divisible by 2 (853x480)
  Error initializing output stream

  If i use for first representation 478p ffmpeg run correctly all two encoding but after when i try to load these two files on MP4Box to dash them live with the following command :

  MP4Box -dash-live 8000 -subdur 8000 -profile dashavc264:live -mpd-refresh 240.0 -time-shift 24 -min-buffer 4000 -insert-utc -no-cache -out manifest.mpd format1080.mp4#video format480.mp4#video format1080.mp4#audio format480.mp4#audio

  the error come back into mp4box :
  "files have not-proportional layout 1920 x 1080 vs 849 x 478 but sample size and aspect ratio match, assuming precision issue"

  I would like to understand what i don’t know about, which are the resolutions that match, i understand that some movies have atypical resolution for example 1040 or 432 but the input video for this test is correct 1920 X 1080 and i wish to compress/encode it for dash and to create another representation with 480p, could i ask where I’m wrong ?
  Thanks !
  Massimo