add control over encoder

- selectable H.264 profile
- configurable B frames
- configurable average bitrate

There are more configuration possibilities but it should be enough for me now

README.md

@@ -107,7 +107,8 @@ There are just 4 functions and 3 user-visible data types:
 - `hve_close`
 
 ```C
-	struct hve_config hardware_config = {WIDTH, HEIGHT, FRAMERATE, DEVICE, PIXEL_FORMAT};
+	struct hve_config hardware_config = {WIDTH, HEIGHT, FRAMERATE, DEVICE,
+													PIXEL_FORMAT, PROFILE, BFRAMES, BITRATE};
 	struct hve *hardware_encoder=hve_init(&hardware_config);
 	struct hve_frame frame = { 0 };
 

examples/hve_encode_raw_h264.c

@@ -20,6 +20,9 @@ const int FRAMERATE=30;
 int SECONDS=10;
 const char *DEVICE=NULL; //NULL for default or device e.g. "/dev/dri/renderD128"
 const char *PIXEL_FORMAT="nv12"; //NULL for default (NV12) or pixel format e.g. "rgb0"
+const int PROFILE=FF_PROFILE_H264_HIGH; //or FF_PROFILE_H264_MAIN, FF_PROFILE_H264_CONSTRAINED_BASELINE, ...
+const int BFRAMES=0; //max_b_frames, set to 0 to minimize latency, non-zero to minimize size
+const int BITRATE=0; //average bitrate in VBR
 
 int encoding_loop(struct hve *hardware_encoder, FILE *output_file);
 int process_user_input(int argc, char* argv[]);
@@ -33,7 +36,7 @@ int main(int argc, char* argv[])
 		return -1;
 
 	//prepare library data
-	struct hve_config hardware_config = {WIDTH, HEIGHT, FRAMERATE, DEVICE, PIXEL_FORMAT};
+	struct hve_config hardware_config = {WIDTH, HEIGHT, FRAMERATE, DEVICE, PIXEL_FORMAT, PROFILE, BFRAMES, BITRATE};
 	struct hve *hardware_encoder;
 
 	//prepare file for raw H.264 output

hve.c

@@ -75,6 +75,11 @@ struct hve *hve_init(const struct hve_config *config)
 	h->avctx->sample_aspect_ratio = (AVRational){ 1, 1 };
 	h->avctx->pix_fmt = AV_PIX_FMT_VAAPI;
 
+	if(config->profile)
+		h->avctx->profile = config->profile;
+	h->avctx->max_b_frames = config->max_b_frames;
+	h->avctx->bit_rate = config->bit_rate;
+
 	//try to find software pixel format that user wants to upload data in
 	if(config->pixel_format == NULL)
 		h->sw_pix_fmt = AV_PIX_FMT_NV12;

hve.h

@@ -68,6 +68,23 @@ struct hve;
  * For pixel format explanation see:
  * <a href="https://ffmpeg.org/doxygen/3.4/pixfmt_8h.html#a9a8e335cf3be472042bc9f0cf80cd4c5">FFmpeg pixel formats</a>
  *
+ * The profile (H.264 profile) can typically be:
+ * - FF_PROFILE_H264_CONSTRAINED_BASELINE
+ * - FF_PROFILE_H264_MAIN
+ * - FF_PROFILE_H264_HIGH
+ * - ...
+ *
+ * You may check profiles supported by your hardware with vainfo:
+ * @code
+ * vainfo --display drm --device /dev/dri/renderDXYZ
+ * @endcode
+ *
+ * The max_b_frames controls the number of B frames.
+ * Disable B frames if you need low latency (at the cost of space).
+ * The output will be delayed by max_b_frames+1 relative to the input.
+ *
+ * The bit_rate is average bitrate in VBR mode.
+ *
  * @see hve_init
  */
 struct hve_config
@@ -77,6 +94,9 @@ struct hve_config
 	int framerate; //!< framerate of the encoded video
 	const char *device; //!< NULL or device, e.g. "/dev/dri/renderD128"
 	const char *pixel_format; //!< NULL for NV12 or format, e.g. "rgb0", "bgr0", "nv12", "yuv420p"
+	int profile; //!< 0 to guess from input or profile e.g. FF_PROFILE_H264_MAIN, FF_PROFILE_H264_HIGH
+	int max_b_frames; //!< maximum number of B-frames between non-B-frames (disable if you need low latency)
+	int bit_rate; //!< the average bitrate in VBR mode
 };
 
 /**