Adds an option to use constant bitrate instead of average bitrate to the
videotoolbox encoders. This is enabled via -constant_bit_rate true.
macOS 13 is required for this option to work.
Signed-off-by: Sebastian Beckmann <beckmann.sebast...@outlook.de>
---
Changes the name of vtenc_constant_bit_rate_enabled to
vtenc_constant_bit_rate_available to clarify that this checks for
availablity of the feature.
libavcodec/videotoolboxenc.c | 37 +++++++++++++++++++++++++++++++++---
1 file changed, 34 insertions(+), 3 deletions(-)
diff --git a/libavcodec/videotoolboxenc.c b/libavcodec/videotoolboxenc.c
index 823e5ad94e..18d68360ef 100644
--- a/libavcodec/videotoolboxenc.c
+++ b/libavcodec/videotoolboxenc.c
@@ -101,6 +101,7 @@ static struct{
CFStringRef kVTCompressionPropertyKey_RealTime;
CFStringRef kVTCompressionPropertyKey_TargetQualityForAlpha;
CFStringRef kVTCompressionPropertyKey_PrioritizeEncodingSpeedOverQuality;
+ CFStringRef kVTCompressionPropertyKey_ConstantBitRate;
CFStringRef
kVTVideoEncoderSpecification_EnableHardwareAcceleratedVideoEncoder;
CFStringRef
kVTVideoEncoderSpecification_RequireHardwareAcceleratedVideoEncoder;
@@ -164,6 +165,7 @@ static void loadVTEncSymbols(){
"TargetQualityForAlpha");
GET_SYM(kVTCompressionPropertyKey_PrioritizeEncodingSpeedOverQuality,
"PrioritizeEncodingSpeedOverQuality");
+ GET_SYM(kVTCompressionPropertyKey_ConstantBitRate, "ConstantBitRate");
GET_SYM(kVTVideoEncoderSpecification_EnableHardwareAcceleratedVideoEncoder,
"EnableHardwareAcceleratedVideoEncoder");
@@ -236,6 +238,7 @@ typedef struct VTEncContext {
int realtime;
int frames_before;
int frames_after;
+ bool constant_bit_rate;
int allow_sw;
int require_sw;
@@ -1073,12 +1076,22 @@ static bool vtenc_qscale_enabled(void)
return !TARGET_OS_IPHONE && TARGET_CPU_ARM64;
}
+// constant bit rate only on Macs with Apple Silicon running macOS 13
(Ventura) or newer
+static bool vtenc_constant_bit_rate_available(void)
+{
+ if (__builtin_available(macOS 13, *))
+ return !TARGET_OS_IPHONE && TARGET_CPU_ARM64;
+ else
+ return false;
+}
+
static int vtenc_create_encoder(AVCodecContext *avctx,
CMVideoCodecType codec_type,
CFStringRef profile_level,
CFNumberRef gamma_level,
CFDictionaryRef enc_info,
CFDictionaryRef pixel_buffer_info,
+ bool constant_bit_rate,
VTCompressionSessionRef *session)
{
VTEncContext *vtctx = avctx->priv_data;
@@ -1122,6 +1135,11 @@ static int vtenc_create_encoder(AVCodecContext *avctx,
return AVERROR_EXTERNAL;
}
+ if (constant_bit_rate && !vtenc_constant_bit_rate_available()) {
+ av_log(avctx, AV_LOG_ERROR, "Error: -constant_bit_rate true not
available for encoder.\n");
+ return AVERROR_EXTERNAL;
+ }
+
if (avctx->flags & AV_CODEC_FLAG_QSCALE) {
quality = quality >= 100 ? 1.0 : quality / 100;
quality_num = CFNumberCreate(kCFAllocatorDefault,
@@ -1139,9 +1157,16 @@ static int vtenc_create_encoder(AVCodecContext *avctx,
&bit_rate);
if (!bit_rate_num) return AVERROR(ENOMEM);
- status = VTSessionSetProperty(vtctx->session,
- kVTCompressionPropertyKey_AverageBitRate,
- bit_rate_num);
+ if (constant_bit_rate) {
+ status = VTSessionSetProperty(vtctx->session,
+
compat_keys.kVTCompressionPropertyKey_ConstantBitRate,
+ bit_rate_num);
+ } else {
+ status = VTSessionSetProperty(vtctx->session,
+
kVTCompressionPropertyKey_AverageBitRate,
+ bit_rate_num);
+ }
+
CFRelease(bit_rate_num);
}
@@ -1530,6 +1555,7 @@ static int vtenc_configure_encoder(AVCodecContext *avctx)
gamma_level,
enc_info,
pixel_buffer_info,
+ vtctx->constant_bit_rate,
&vtctx->session);
init_cleanup:
@@ -2532,6 +2558,7 @@ static int vtenc_populate_extradata(AVCodecContext
*avctx,
gamma_level,
enc_info,
pixel_buffer_info,
+ vtctx->constant_bit_rate,
&vtctx->session);
if (status)
goto pe_cleanup;
@@ -2727,6 +2754,8 @@ static const AVOption h264_options[] = {
{ "a53cc", "Use A53 Closed Captions (if available)", OFFSET(a53_cc),
AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 1, VE },
+ { "constant_bit_rate", "Require constant bit rate (macOS 13 or newer)",
OFFSET(constant_bit_rate), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, VE },
+
COMMON_OPTIONS
{ NULL },
};
@@ -2760,6 +2789,8 @@ static const AVOption hevc_options[] = {
{ "alpha_quality", "Compression quality for the alpha channel",
OFFSET(alpha_quality), AV_OPT_TYPE_DOUBLE, { .dbl = 0.0 }, 0.0, 1.0, VE },
+ { "constant_bit_rate", "Require constant bit rate (macOS 13 or newer)",
OFFSET(constant_bit_rate), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, VE },
+
COMMON_OPTIONS
{ NULL },
};
--
2.37.0 (Apple Git-136)
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