[FFmpeg-devel] [PATCH] videotoolboxenc: enable constant quality with -q:v on Apple Silicon Macs and use b-frames für HEVC and H264 and b-pyramid for HEVC.

[simone at lisanet.de]

From: Simone Karin Lehmann <simone at lisanet.de>

Signed-off-by: Simone Karin Lehmann <simone at lisanet.de>
---
 libavcodec/videotoolboxenc.c | 54 ++++++++++++++++++++++++++++--------
 1 file changed, 42 insertions(+), 12 deletions(-)

diff --git a/libavcodec/videotoolboxenc.c b/libavcodec/videotoolboxenc.c
index 400401550a..e8cbc9dd4d 100644
--- a/libavcodec/videotoolboxenc.c
+++ b/libavcodec/videotoolboxenc.c
@@ -224,7 +224,7 @@ typedef struct VTEncContext {
     int64_t require_sw;
 
     bool flushing;
-    bool has_b_frames;
+    int has_b_frames;
     bool warned_color_range;
 
     /* can't be bool type since AVOption will access it as int */
@@ -1014,6 +1014,12 @@ static int get_cv_ycbcr_matrix(AVCodecContext *avctx, CFStringRef *matrix) {
     return 0;
 }
 
+// constant quality only on Macs with Apple Silicon
+static bool vtenc_qscale_enabled(void)
+{
+    return TARGET_OS_OSX && TARGET_CPU_ARM64;
+}
+
 static int vtenc_create_encoder(AVCodecContext   *avctx,
                                 CMVideoCodecType codec_type,
                                 CFStringRef      profile_level,
@@ -1025,7 +1031,9 @@ static int vtenc_create_encoder(AVCodecContext   *avctx,
     VTEncContext *vtctx = avctx->priv_data;
     SInt32       bit_rate = avctx->bit_rate;
     SInt32       max_rate = avctx->rc_max_rate;
+    Float32      quality = avctx->global_quality / FF_QP2LAMBDA;
     CFNumberRef  bit_rate_num;
+    CFNumberRef  quality_num;
     CFNumberRef  bytes_per_second;
     CFNumberRef  one_second;
     CFArrayRef   data_rate_limits;
@@ -1056,15 +1064,33 @@ static int vtenc_create_encoder(AVCodecContext   *avctx,
         return AVERROR_EXTERNAL;
     }
 
-    bit_rate_num = CFNumberCreate(kCFAllocatorDefault,
-                                  kCFNumberSInt32Type,
-                                  &bit_rate);
-    if (!bit_rate_num) return AVERROR(ENOMEM);
+    if (avctx->flags & AV_CODEC_FLAG_QSCALE && !vtenc_qscale_enabled()) {
+        av_log(avctx, AV_LOG_ERROR, "Error: -q:v qscale not available for encoder. Use -b:v bitrate instead.\n");
+        return AVERROR_EXTERNAL;
+    }
+
+    if (avctx->flags & AV_CODEC_FLAG_QSCALE) {
+        quality = quality >= 100 ? 1.0 : quality / 100;
+        quality_num = CFNumberCreate(kCFAllocatorDefault,
+                                     kCFNumberFloat32Type,
+                                     &quality);
+        if (!quality_num) return AVERROR(ENOMEM);
 
-    status = VTSessionSetProperty(vtctx->session,
-                                  kVTCompressionPropertyKey_AverageBitRate,
-                                  bit_rate_num);
-    CFRelease(bit_rate_num);
+        status = VTSessionSetProperty(vtctx->session,
+                                      kVTCompressionPropertyKey_Quality,
+                                      quality_num);
+        CFRelease(quality_num);
+    } else {
+        bit_rate_num = CFNumberCreate(kCFAllocatorDefault,
+                                      kCFNumberSInt32Type,
+                                      &bit_rate);
+        if (!bit_rate_num) return AVERROR(ENOMEM);
+
+        status = VTSessionSetProperty(vtctx->session,
+                                      kVTCompressionPropertyKey_AverageBitRate,
+                                      bit_rate_num);
+        CFRelease(bit_rate_num); 
+    }
 
     if (status) {
         av_log(avctx, AV_LOG_ERROR, "Error setting bitrate property: %d\n", status);
@@ -1333,6 +1359,7 @@ static int vtenc_configure_encoder(AVCodecContext *avctx)
     }
 
     vtctx->codec_id = avctx->codec_id;
+    avctx->max_b_frames = 16;
 
     if (vtctx->codec_id == AV_CODEC_ID_H264) {
         vtctx->get_param_set_func = CMVideoFormatDescriptionGetH264ParameterSetAtIndex;
@@ -1340,7 +1367,7 @@ static int vtenc_configure_encoder(AVCodecContext *avctx)
         vtctx->has_b_frames = avctx->max_b_frames > 0;
         if(vtctx->has_b_frames && vtctx->profile == H264_PROF_BASELINE){
             av_log(avctx, AV_LOG_WARNING, "Cannot use B-frames with baseline profile. Output will not contain B-frames.\n");
-            vtctx->has_b_frames = false;
+            vtctx->has_b_frames = 0;
         }
 
         if (vtctx->entropy == VT_CABAC && vtctx->profile == H264_PROF_BASELINE) {
@@ -1353,6 +1380,8 @@ static int vtenc_configure_encoder(AVCodecContext *avctx)
         vtctx->get_param_set_func = compat_keys.CMVideoFormatDescriptionGetHEVCParameterSetAtIndex;
         if (!vtctx->get_param_set_func) return AVERROR(EINVAL);
         if (!get_vt_hevc_profile_level(avctx, &profile_level)) return AVERROR(EINVAL);
+        // HEVC has b-byramid
+        vtctx->has_b_frames = avctx->max_b_frames > 0 ? 2 : 0;
     }
 
     enc_info = CFDictionaryCreateMutable(
@@ -1448,7 +1477,8 @@ static av_cold int vtenc_init(AVCodecContext *avctx)
 
     if (!status && has_b_frames_cfbool) {
         //Some devices don't output B-frames for main profile, even if requested.
-        vtctx->has_b_frames = CFBooleanGetValue(has_b_frames_cfbool);
+        // HEVC has b-pyramid
+        vtctx->has_b_frames = (CFBooleanGetValue(has_b_frames_cfbool) && avctx->codec_id == AV_CODEC_ID_HEVC) ? 2 : 1;
         CFRelease(has_b_frames_cfbool);
     }
     avctx->has_b_frames = vtctx->has_b_frames;
@@ -2356,7 +2386,7 @@ static av_cold int vtenc_frame(
 
         if (vtctx->frame_ct_in == 0) {
             vtctx->first_pts = frame->pts;
-        } else if(vtctx->frame_ct_in == 1 && vtctx->has_b_frames) {
+        } else if(vtctx->frame_ct_in == vtctx->has_b_frames) {
             vtctx->dts_delta = frame->pts - vtctx->first_pts;
         }
 
-- 
2.24.3 (Apple Git-128)