Re: [FFmpeg-devel] [Internet][PATCH v2 00/12] Add MediaCodec encoder and NDK MediaCodec support

[Zhao Zhili <quinkblack@foxmail.com>]

On Sun, 2022-11-20 at 14:49 +0800, Zhao Zhili wrote:
> From: Zhao Zhili <zhilizhao@tencent.com>
> 
> 
> v2:
> 
> Rebased on master.
> 
> 01/12: Use crop-width/crop-height as fallback and add TODO. Co-
> authored-by: Aman Karmani 
> 07/12: Fix libavcodec/version.h conflict
> 10/12: Change default i-frame-interval to 1 and add log message; bump
> minor version
> 12/12: Fix rebase conflict
> 
> 
> v1:
> Firstly, some bugs were fixed (patch 1-4).
> 
> Patch 5 and 6 make mediacodec_wrapper support Java MediaCodec and NDK
> MediaCodec. The use case I'm considering is run FFmpeg on cmdline
> without JVM,
> for example, run FFmpeg inside of termux (an Android terminal
> emulator). It's
> well known that NDK MediaCodec missing some important functions, like
> get the
> list of codecs, but still useable.
> 
> Patch 7 add NDK MediaCodec decoder support. It can be enabled via
> options,
> and enabled automatically if no JVM is available.
> 
> Patch 8 add ANativeWindow support to hwcontext_mediacodec. It can be
> set by
> user, and can be created via AMediaCodec_createPersistentInputSurface
> automatically. This is a preparation for encoder.
> 
> Patch 9 makes MediaCodec decoder to support ANativeWindow directly.
> It worth
> to note that AVMediaCodecContext has only surface. Although we
> provided
> av_mediacodec_alloc_context(), we didn't strictly prevent users to
> allocate
> AVMediaCodecContext on stack. I'm not sure if it's OK to add new
> field to
> AVMediaCodecContext.
> 
> Patch 10 add MediaCodec encoder support. Frame can be feed to encoder
> via
> buffer, or via Surface/ANativeWindow. If Surface/ANativeWindow is
> used, and
> the frames come from our MediaCodec decoder wrapper, we can control
> it's
> 'render' (send to encoder's surface) via
> av_mediacodec_release_buffer(). A DTS
> generation strategy works in this case. However, if frames comes from
> other
> sources, like a camera, there is no way to control the 'render' yet,
> so DTS is
> missing in this case.
> 
> Finally, we can do mediacodec transcoding with FFmpeg cmdline on
> Android.
> More importantly, we can do MediaCodec decoder to encoder without
> copy frames,
> although it's very limited since most of avfilters doesn't work. For
> example:
> 
> ./ffmpeg -hwaccel mediacodec -hwaccel_output_format mediacodec -i
> /sdcard/test.mp4 -an -c:v h264_mediacodec -y /sdcard/out.mp4
> 
> Since there is no real AVHWFrameContext implementation in
> hwcontext_mediacodec.
> there is no hwframe_ctx for mediacodec and av_hwframe_transfer_data()
> doesn't
> work. So if -hwaccel_output_format isn't being specified like:
> 
> ./ffmpeg -hwaccel mediacodec -i /sdcard/test.mp4 -an -c:v
> h264_mediacodec -y /sdcard/out.mp4
> 
> It will trigger a crash in av_hwframe_transfer_data. Patch 11 add a
> check on
> hwframe_ctx. Patch 12 set hwaccel_output_format automatically to
> avoid such
> case.
> 

Applied.

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