On 2017/10/31 23:45, Mark Thompson wrote:
> On 31/10/17 15:11, Jun Zhao wrote:> On 2017/10/31 18:19, Mark Thompson wrote:
>>> On 31/10/17 02:37, Jun Zhao wrote:
>>>> From 7eef9be1c8a92bf625d62a0f97f762f1342c6d78 Mon Sep 17 00:00:00 2001
>>>> From: Jun Zhao <jun.z...@intel.com>
>>>> Date: Tue, 31 Oct 2017 10:13:42 +0800
>>>> Subject: [PATCH 1/2] lavc/vaapi_encode: correct the HRD buffer size
>>>> calculate.
>>>>
>>>> when rc_buffer_size didn't setting, always use the max bit rate
>>>> per second as HRD buffer size.
>>>>
>>>> Signed-off-by: Jun Zhao <jun.z...@intel.com>
>>>> Signed-off-by: Wang, Yi A <yi.a.w...@intel.com>
>>>> ---
>>>> libavcodec/vaapi_encode.c | 21 ++++++++++-----------
>>>> 1 file changed, 10 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/libavcodec/vaapi_encode.c b/libavcodec/vaapi_encode.c
>>>> index 590f4be4ed..d5f89ef346 100644
>>>> --- a/libavcodec/vaapi_encode.c
>>>> +++ b/libavcodec/vaapi_encode.c
>>>> @@ -1144,19 +1144,9 @@ static av_cold int
>>>> vaapi_encode_init_rate_control(AVCodecContext *avctx)
>>>> return AVERROR(EINVAL);
>>>> }
>>>>
>>>> - if (avctx->rc_buffer_size)
>>>> - hrd_buffer_size = avctx->rc_buffer_size;
>>>> - else
>>>> - hrd_buffer_size = avctx->bit_rate;
>>>> - if (avctx->rc_initial_buffer_occupancy)
>>>> - hrd_initial_buffer_fullness = avctx->rc_initial_buffer_occupancy;
>>>> - else
>>>> - hrd_initial_buffer_fullness = hrd_buffer_size * 3 / 4;
>>>> -
>>>> if (ctx->va_rc_mode == VA_RC_CBR) {
>>>> rc_bits_per_second = avctx->bit_rate;
>>>> rc_target_percentage = 100;
>>>> - rc_window_size = 1000;
>>>> } else {
>>>> if (avctx->rc_max_rate < avctx->bit_rate) {
>>>> // Max rate is unset or invalid, just use the normal bitrate.
>>>> @@ -1166,8 +1156,17 @@ static av_cold int
>>>> vaapi_encode_init_rate_control(AVCodecContext *avctx)
>>>> rc_bits_per_second = avctx->rc_max_rate;
>>>> rc_target_percentage = (avctx->bit_rate * 100) /
>>>> rc_bits_per_second;
>>>> }
>>>> - rc_window_size = (hrd_buffer_size * 1000) / avctx->bit_rate;
>>>> }
>>>> + rc_window_size = (rc_bits_per_second * 1000) / avctx->bit_rate;
>>>> +
>>>> + if (avctx->rc_buffer_size)
>>>> + hrd_buffer_size = avctx->rc_buffer_size;
>>>> + else
>>>> + hrd_buffer_size = rc_bits_per_second;
>>>> + if (avctx->rc_initial_buffer_occupancy)
>>>> + hrd_initial_buffer_fullness = avctx->rc_initial_buffer_occupancy;
>>>> + else
>>>> + hrd_initial_buffer_fullness = hrd_buffer_size * 3 / 4;
>>>>
>>>> ctx->rc_params.misc.type = VAEncMiscParameterTypeRateControl;
>>>> ctx->rc_params.rc = (VAEncMiscParameterRateControl) {
>>>> --
>>>> 2.14.1
>>>>
>>> Why? If the RC buffer size is unset it currently guesses one second of the
>>> target bitrate - in what way is the peak bitrate any more appropriate as a
>>> guess?
>> In VBR mode, when rc_max_rate more than bit_rate, I think HDR size need
>> to use rc_max_rate, not the bit_rate.
> Ok, why do you think that? I'm not necessarily against this change (in cases
> where it matters the user will provide rc_buffer_size explicitly), but please
> provide some reasoning for it.
I think the code logic have considered the explicit rc_buffer_size
setting, and this patch
correct the HRD buffer size with MAX(rc_max_rate, bit_rate) when no
setting rc_buffer_size in
VBR mode. In the old logic, in VBR mode, if user don't setting
rc_buffer_size
explicitly, the HRD buffer size always use avctx->bit_rate, it does not
make sense.
>
> - Mark
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