If a JNI environment is not already attached to the thread where the
MediaCodec calls are made the current implementation will attach /
detach an environment for each MediaCodec call wasting some CPU time.
ff_jni_get_env replaces ff_jni_{attach,detach} by permanently attaching
an environment (if it is not already the case) to the current thread.
The environment will be automatically detached at the thread destruction
using a pthread_key callback.
Saves around 5% of CPU time (out of 20%) while decoding a stream with
MediaCodec.
Allows to select a codec (encoder or decoder) only if it supports a
specific profile.
Adds ff_AMediaCodecProfile_getProfileFromAVCodecContext to convert an
AVCodecContext profile to a MediaCodec profile. It only supports H264
for now.
The codepath using MediaCodecList.findDecoderForFormat() (Android >= 5.0)
has been dropped as this method does not allow to select a decoder
compatible with a specific profile.
Codec width/height restrictions seem hardcoded at the OMX level and
seem arbitrary. Bypassing those restrictions allows a device to decode
streams at higher resolutions.
For example it allows a Nexus 5 to decode h264 streams with a resolution
higher than 1920x1080.
