On Fri, Aug 26, 2022 at 1:42 PM Sebastian Beckmann
<beckmann.sebast...@outlook.de> wrote:
>
> 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>
> ---
> libavcodec/videotoolboxenc.c | 37 +++++++++++++++++++++++++++++++++---
> 1 file changed, 34 insertions(+), 3 deletions(-)
>
> diff --git a/libavcodec/videotoolboxenc.c b/libavcodec/videotoolboxenc.c
> index 823e5ad94e..9eb6fe09a2 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_enabled(void)
> +{
> + if (__builtin_available(macOS 13, *))
> + return !TARGET_OS_IPHONE && TARGET_CPU_ARM64;
> + else
> + return false;
> +}
vtenc_constant_bit_rate_available() may be a better name for this
function, its the user that enables it through the flag you added
> 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_enabled()) {
> + 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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