On 1/8/23, Michael Niedermayer <mich...@niedermayer.cc> wrote: > On Fri, Jan 06, 2023 at 07:04:59PM +0100, Paul B Mahol wrote: >> On Fri, Jan 6, 2023 at 7:01 PM Paul B Mahol <one...@gmail.com> wrote: >> >> > >> > >> > On Fri, Jan 6, 2023 at 6:25 PM Michael Niedermayer >> > <mich...@niedermayer.cc> >> > wrote: >> > >> >> On Thu, Jan 05, 2023 at 11:08:25PM +0100, Paul B Mahol wrote: >> >> > On Thu, Jan 5, 2023 at 9:53 PM Michael Niedermayer < >> >> mich...@niedermayer.cc> >> >> > wrote: >> >> > >> >> > > On Thu, Jan 05, 2023 at 01:44:10PM +0100, Paul B Mahol wrote: >> >> > > > Patch attached. >> >> > > >> >> > > > swresample.c | 3 ++- >> >> > > > 1 file changed, 2 insertions(+), 1 deletion(-) >> >> > > > eee7a0685b44aa867562138a2e2437ecb8844612 >> >> > > 0001-libswresample-swresample-avoid-s16p-internal-transfe.patch >> >> > > > From 9c4cd60e2dd41cf98d693c8251f4cfade0807073 Mon Sep 17 >> >> > > > 00:00:00 >> >> 2001 >> >> > > > From: Paul B Mahol <one...@gmail.com> >> >> > > > Date: Thu, 5 Jan 2023 13:40:12 +0100 >> >> > > > Subject: [PATCH] libswresample/swresample: avoid s16p internal >> >> transfer >> >> > > format >> >> > > > >> >> > > > Instead use float one by default for sample rate conversions. >> >> > > > The s16p internal transfer format produces visible and hearable >> >> > > > quantization artifacts. >> >> > > >> >> > > When does this occur and why? >> >> > > >> >> > >> >> > It occurs always. Just compare output with 16bit and >> >> > int32/float/double. >> >> > Look at other people report on internet. >> >> > Look at src.infinitewave.ca >> >> >> >> src.infinitewave.ca uses 32bit none of what it shows should touch the >> >> codepath >> >> you change. >> >> >> >> if we look at src.infinitewave.ca for swr we see 2 types of artifacts >> >> 1. Aliassing which is at maybe -120db with the actual signal at 0db >> >> i would like to see some evidence that a human can hear this >> >> >> > >> > For s16p<->s16p it is much lower, around -78dB thus this patch. >> > >> > Also for others and reports for swr its is lower than exact -120dB >> > >> > >> > 2. Reflection and attenuation at the transition frequency >> >> With linear filters there is a tradeof between attenuation of the >> >> passband, reflection of frequencies beyond, latency and so on >> >> You can have a perfect sharp cutoff with no attenuation and no >> >> refelection >> >> that requires a infinitly long filter. And while this looks best in >> >> this >> >> frequency plot, does it actually sound best ? If you can hear -120db >> >> signals you surely would then also hear the ringing long before a >> >> gunshot >> >> from such long filter. >> >> >> > >> One can always change linear FIR to be min phase FIR kernel. > > I certainly would welcome a wider range of filters in swr, if you want to > add > any low delay sinc approximation or in fact i would welcome any filter > you want to add.
I have hack for simple cases when one of decimation/interpolation factor is 1 than there is single only FIR kernel applied and then one do not use naive convolution which is O(N^2) but O(Nlog(N)) when using RDFT/FFT. For bigger filter sizes it makes filtering amazingly faster. (from <80x to >400x). So I'm interested in making it faster if possible for any combination of decimation/interpolation. > > thx > > [...] > -- > Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB > > The real ebay dictionary, page 1 > "Used only once" - "Some unspecified defect prevented a second use" > "In good condition" - "Can be repaird by experienced expert" > "As is" - "You wouldnt want it even if you were payed for it, if you knew > ..." > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
