[FFmpeg-devel] [PATCH] Implement hdcd filtering

[Michael Niedermayer]

On Tue, Mar 29, 2016 at 11:30:28AM +0200, Benjamin St wrote:
> > Not all of the comments on top of the filter file look
> > very useful to me, what do you think?
> > In any case, I'd say a link to these should be useful:
> > http://www.audiomisc.co.uk/HFN/HDCD/Enigma.html
> > http://www.audiomisc.co.uk/HFN/HDCD/Examined.html
> > (Or only the second one.)
> >
> I removed the rather useless comment and added both links.
> 
> Please also add a fate test, since this is using floats,
> > I would suggest to only compare pcm_s16 (instead of 24).
> 
> Floats are no longer needed. This version uses only integer.

>  Makefile     |    1 
>  af_hdcd.c    | 1138 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  allfilters.c |    1 
>  3 files changed, 1140 insertions(+)
> 4e25a0315a659eb9e71adfacb9f9b2e78c5e1f33  0001-Implement-high-definition-audio-cd-filtering.patch
> From f3053beac96884123e1c9d50b46876e6f69ae0d1 Mon Sep 17 00:00:00 2001
> From: Benjamin Steffes <benjaminst123 at gmail.com>
> Date: Mon, 21 Mar 2016 23:52:48 +0100
> Subject: [PATCH] Implement high definition audio cd filtering.
> 
> Signed-off-by: Benjamin Steffes <benjaminst123 at gmail.com>
> ---
>  libavfilter/Makefile     |    1 +
>  libavfilter/af_hdcd.c    | 1138 ++++++++++++++++++++++++++++++++++++++++++++++
>  libavfilter/allfilters.c |    1 +
>  3 files changed, 1140 insertions(+)
>  create mode 100644 libavfilter/af_hdcd.c

Changelog entry and docs update missing

a fate test would still be interresting i think

has this been tested against some reference / known to be correct
output for some stream ?

[...]

> +static int integrate(hdcd_state_t *state, int *flag, int const *samples, int count, int stride)
> +{
> +    uint32_t bits = 0;
> +    int result = FFMIN(state->readahead, count);
> +    int i;
> +    *flag = 0;
> +
> +    for (i = result - 1; i >= 0; i--) {
> +        bits |= (*samples & 1) << i; /* might be better as a conditional? */
> +        samples += stride;
> +    }
> +
> +    state->window = (state->window << result) | bits;
> +    state->readahead -= result;
> +    if (state->readahead > 0)
> +        return result;
> +

> +    bits = (state->window ^ state->window >> 5 ^ state->window >> 23) & 0xffffffffu;

the & 0xffffffffu; seems redundant


[...]
> +static int filter_frame(AVFilterLink *inlink, AVFrame *in)
> +{
> +    AVFilterContext *ctx = inlink->dst;
> +    HDCDContext *s = ctx->priv;
> +    AVFilterLink *outlink = ctx->outputs[0];
> +    AVFrame *out;

> +    int16_t *in_data;

const

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No snowflake in an avalanche ever feels responsible. -- Voltaire
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