[FFmpeg-devel] [PATCH 5/6] avcodec/qtrle: return last frame even if unchanged
Michael Niedermayer
michael at niedermayer.cc
Mon Aug 26 10:32:52 EEST 2019
On Sun, Aug 25, 2019 at 08:04:03PM -0300, James Almer wrote:
> On 8/25/2019 6:46 PM, Michael Niedermayer wrote:
> > On Sun, Aug 25, 2019 at 01:22:22PM -0300, James Almer wrote:
> >> On 8/24/2019 3:18 PM, Michael Niedermayer wrote:
> >>> Fixes: Ticket7880
> >>>
> >>> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> >>> ---
> >>> libavcodec/qtrle.c | 30 ++++++++++++++++++++++++++----
> >>> tests/ref/fate/qtrle-8bit | 1 +
> >>> 2 files changed, 27 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/libavcodec/qtrle.c b/libavcodec/qtrle.c
> >>> index 2c29547e5a..c22a1a582d 100644
> >>> --- a/libavcodec/qtrle.c
> >>> +++ b/libavcodec/qtrle.c
> >>> @@ -45,6 +45,7 @@ typedef struct QtrleContext {
> >>>
> >>> GetByteContext g;
> >>> uint32_t pal[256];
> >>> + AVPacket flush_pkt;
> >>> } QtrleContext;
> >>>
> >>> #define CHECK_PIXEL_PTR(n) \
> >>> @@ -454,11 +455,27 @@ static int qtrle_decode_frame(AVCodecContext *avctx,
> >>> int has_palette = 0;
> >>> int ret, size;
> >>>
> >>> + if (!avpkt->data) {
> >>> + if (avctx->internal->need_flush) {
> >>> + avctx->internal->need_flush = 0;
> >>> + ret = ff_setup_buffered_frame_for_return(avctx, data, s->frame, &s->flush_pkt);
> >>> + if (ret < 0)
> >>> + return ret;
> >>> + *got_frame = 1;
> >>> + }
> >>> + return 0;
> >>> + }
> >>> + s->flush_pkt = *avpkt;
> >>> + s->frame->pkt_dts = s->flush_pkt.dts;
> >>> +
> >>> bytestream2_init(&s->g, avpkt->data, avpkt->size);
> >>>
> >>> /* check if this frame is even supposed to change */
> >>> - if (avpkt->size < 8)
> >>> + if (avpkt->size < 8) {
> >>> + avctx->internal->need_flush = 1;
> >>> return avpkt->size;
> >>> + }
> >>> + avctx->internal->need_flush = 0;
> >>>
> >>> /* start after the chunk size */
> >>> size = bytestream2_get_be32(&s->g) & 0x3FFFFFFF;
> >>> @@ -471,14 +488,18 @@ static int qtrle_decode_frame(AVCodecContext *avctx,
> >>>
> >>> /* if a header is present, fetch additional decoding parameters */
> >>> if (header & 0x0008) {
> >>> - if (avpkt->size < 14)
> >>> + if (avpkt->size < 14) {
> >>> + avctx->internal->need_flush = 1;
> >>> return avpkt->size;
> >>> + }
> >>> start_line = bytestream2_get_be16(&s->g);
> >>> bytestream2_skip(&s->g, 2);
> >>> height = bytestream2_get_be16(&s->g);
> >>> bytestream2_skip(&s->g, 2);
> >>> - if (height > s->avctx->height - start_line)
> >>> + if (height > s->avctx->height - start_line) {
> >>> + avctx->internal->need_flush = 1;
> >>> return avpkt->size;
> >>> + }
> >>> } else {
> >>> start_line = 0;
> >>> height = s->avctx->height;
> >>> @@ -572,5 +593,6 @@ AVCodec ff_qtrle_decoder = {
> >>> .init = qtrle_decode_init,
> >>> .close = qtrle_decode_end,
> >>> .decode = qtrle_decode_frame,
> >>> - .capabilities = AV_CODEC_CAP_DR1,
> >>> + .caps_internal = FF_CODEC_CAP_SETS_PKT_DTS | FF_CODEC_CAP_SETS_PKT_POS,
> >>> + .capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY,
> >>> };
> >>> diff --git a/tests/ref/fate/qtrle-8bit b/tests/ref/fate/qtrle-8bit
> >>> index 27bb8aad71..39a03b7b6c 100644
> >>> --- a/tests/ref/fate/qtrle-8bit
> >>> +++ b/tests/ref/fate/qtrle-8bit
> >>> @@ -61,3 +61,4 @@
> >>> 0, 160, 160, 1, 921600, 0xcfd6ad2b
> >>> 0, 163, 163, 1, 921600, 0x3b372379
> >>> 0, 165, 165, 1, 921600, 0x36f245f5
> >>> +0, 166, 166, 1, 921600, 0x36f245f5
> >>
> >> Following what i said in the nuv patch, do you still experience timeouts
> >> with the current codebase, or even if you revert commit
> >> a9dacdeea6168787a142209bd19fdd74aefc9dd6? Creating a reference to an
> >> existing frame buffer shouldn't be expensive anymore for the fuzzer
> >> after my ref counting changes to target_dec_fuzzer.c
> >>
> >> This is a very ugly solution to a problem that was already solved when
> >> reference counting was introduced. Returning duplicate frames to achieve
> >> cfr in decoders where it's expected shouldn't affect performance.
> >
> > Maybe i should ask this backward to make it clearer what this is trying
> > to fix.
> >
> > Consider a patch that would return every frame twice with the same ref
> > of course.
> > Would you consider this to have 0 performance impact ?
>
> No, but it would be negligible.
ok, lets see some actual numbers
This comparission is about fixing ticket 7880 (just saying so we dont loose
track of what we compare here)
this qtrle patchset which fixes the last frame
time ./ffmpeg -i clock.mov -vf scale=1920x1080 -qscale 2 -y test-new.avi
real 0m0.233s
user 0m0.404s
sys 0m0.036s
-rw-r----- 1 michael michael 769212 Aug 26 08:38 test-new.avi
time ./ffmpeg -i test-new.avi -f null -
real 0m0.095s
user 0m0.131s
sys 0m0.038s
The alternative of reverting the code that discards duplicate frames
(this i believe is what the people opposing this patchset here want)
git revert a9dacdeea6168787a142209bd19fdd74aefc9dd6
time ./ffmpeg -i clock.mov -vf scale=1920x1080 -qscale 2 -y test.avi
real 0m1.208s
user 0m2.866s
sys 0m0.168s
-rw-r----- 1 michael michael 3274430 Aug 26 08:44 test.avi
time ./ffmpeg -i test.avi -f null -
real 0m0.185s
user 0m0.685s
sys 0m0.076s
https://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket7880/clock.mov
As we can see the solution preferred by the opposition to this patchset
will make the code 6 times slower and result in 4 times higher bitrate for
the same quality.
I would say this is not "negligible"
you know this is not 0.6%, its not 6% its not 60% it is 600%
I do not understand why we have a discussion here about this.
Do we want 600% slower code ?
Do our users want 600% slower code ?
I do not want 600% slower code
Thanks
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
In a rich man's house there is no place to spit but his face.
-- Diogenes of Sinope
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