使用MediaCodec和MTK编解码器编码时选择H264配置文件

Question

We have an Android app that encodes video into H264. On all previously tried Android devices this encodes to Baseline profile which is what I need.

On the Lenovo Yoga 10 the codec is OMX.MTK.VIDEO.ENCODER.AVC. This encodes the video as High Profile which gives a problem for the receiving device.

I am using MediaCodec. There seems to be no way to set the profile to be used.

Is there any way of doing this ? The codec does claim to support Baseline profile but gives no way of using it. Is there a codec specific parameter for this?

Answer 1

What you could try is to add the key profile to your MediaFormat, with a value of 1 ( OMX_VIDEO_AVCProfileBaseline ). If you do this, you probably also need to add the key level with a level value matching your resolution as well (with a value from the OMX AVC level constants).

I'm not sure if this codec actually honors the requested value though, but it might be worth a try.

See the setupAVCEncoderParameters function in https://android.googlesource.com/platform/frameworks/av/+/6ade04174/media/libstagefright/ACodec.cpp for an example on the setup procedure. It looks for the profile key in the input parameters (which are copied from the MediaFormat that you've provided), but if this is present you also need to provide a level parameter, and what level to use depends on your resolution. See https://android.googlesource.com/platform/frameworks/native/+/cde4b13a/include/media/openmax/OMX_Video.h for constant values you can use for the parameters.

But after checking for the profile and level parameters, it also seems to override the profile to baseline regardless of what was set. So either these lines have been removed from your device, or the encoder disregards the h264type.eProfile field altogether.

If someone has got a source tree closer to what actually is used on the devices, it would be even better to inspect that.

As an example on how to pick a suitable level for your resolution, have a look at x264_validate_levels in http://git.videolan.org/?p=x264.git;a=blob;f=encoder/set.c;h=1a40b71284 (but the level passed to MediaFormat needs to be expressed using the OMX_VIDEO_AVCLEVELTYPE constants).

Not sure if anything of this helps, but it's at least worth a try.

Answer 2

Here's a snippet of what I did in my app :

mediaFormat.setInteger("profile", 8); // Profile HIGH
mediaFormat.setInteger("level", 0x200); // Level 3.1

And here are the profile values you can choose from :

OMX_VIDEO_AVCProfileBaseline = 0x01,   /**< Baseline profile */
OMX_VIDEO_AVCProfileMain     = 0x02,   /**< Main profile */
OMX_VIDEO_AVCProfileExtended = 0x04,   /**< Extended profile */
OMX_VIDEO_AVCProfileHigh     = 0x08,   /**< High profile */
OMX_VIDEO_AVCProfileHigh10   = 0x10,   /**< High 10 profile */
OMX_VIDEO_AVCProfileHigh422  = 0x20,   /**< High 4:2:2 profile */
OMX_VIDEO_AVCProfileHigh444  = 0x40,   /**< High 4:4:4 profile */
OMX_VIDEO_AVCProfileKhronosExtensions = 0x6F000000, /**< Reserved region for introducing Khronos Standard Extensions */ 
OMX_VIDEO_AVCProfileVendorStartUnused = 0x7F000000, /**< Reserved region for introducing Vendor Extensions */
OMX_VIDEO_AVCProfileMax      = 0x7FFFFFFF  

And the levels :

OMX_VIDEO_AVCLevel1   = 0x01,     /**< Level 1 */
OMX_VIDEO_AVCLevel1b  = 0x02,     /**< Level 1b */
OMX_VIDEO_AVCLevel11  = 0x04,     /**< Level 1.1 */
OMX_VIDEO_AVCLevel12  = 0x08,     /**< Level 1.2 */
OMX_VIDEO_AVCLevel13  = 0x10,     /**< Level 1.3 */
OMX_VIDEO_AVCLevel2   = 0x20,     /**< Level 2 */
OMX_VIDEO_AVCLevel21  = 0x40,     /**< Level 2.1 */
OMX_VIDEO_AVCLevel22  = 0x80,     /**< Level 2.2 */
OMX_VIDEO_AVCLevel3   = 0x100,    /**< Level 3 */
OMX_VIDEO_AVCLevel31  = 0x200,    /**< Level 3.1 */
OMX_VIDEO_AVCLevel32  = 0x400,    /**< Level 3.2 */
OMX_VIDEO_AVCLevel4   = 0x800,    /**< Level 4 */
OMX_VIDEO_AVCLevel41  = 0x1000,   /**< Level 4.1 */
OMX_VIDEO_AVCLevel42  = 0x2000,   /**< Level 4.2 */
OMX_VIDEO_AVCLevel5   = 0x4000,   /**< Level 5 */
OMX_VIDEO_AVCLevel51  = 0x8000,   /**< Level 5.1 */
OMX_VIDEO_AVCLevelKhronosExtensions = 0x6F000000, /**< Reserved region for introducing Khronos Standard Extensions */ 
OMX_VIDEO_AVCLevelVendorStartUnused = 0x7F000000, /**< Reserved region for introducing Vendor Extensions */
OMX_VIDEO_AVCLevelMax = 0x7FFFFFFF  

It's important to set both.

Answer 3

I have tried this on Nexus 9 with Nvidia HW encoder. Only thing that works for me is to select the encoder by name. I am able to set the profile to chosen value for encoder level is always set to 13.

Please note that if you select encoder by type, it selects google encoder and as mentioned above, it forces profile to baseline.