[FFmpeg-devel] [PATCH] Fixes avcodec_find_best_pix_fmt() with more than 64 pix fmts defined
Matthew Einhorn
moiein2000 at gmail.com
Sun Aug 21 19:22:09 CEST 2011
On Sun, Aug 21, 2011 at 12:09 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Sat, Aug 20, 2011 at 05:06:45PM -0400, Matthew Einhorn wrote:
>> On Fri, Aug 19, 2011 at 6:22 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> > On Wed, Aug 17, 2011 at 08:50:50PM -0400, Matthew Einhorn wrote:
>> >> On Wed, Aug 17, 2011 at 9:32 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> >> > On Wed, Aug 17, 2011 at 10:43:34AM +0200, Stefano Sabatini wrote:
>> >> >> On date Wednesday 2011-08-17 02:38:37 -0400, Matthew Einhorn encoded:
>> >> >> > Hi,
>> >> >> >
>> >> >> > As stated, this patch (attached) should fix
>> >> >> > avcodec_find_best_pix_fmt() so that now with more than 64 pix fmts,
>> >> >> > the function should be able to work for the first 64 fmts. Currently
>> >> >> > the function returns a bad formats, for example,
>> >> >> > avcodec_find_best_pix_fmt(1ULL << PIX_FMT_GRAY8, PIX_FMT_YUV420P, 0,
>> >> >> > &nLoss) returns 72 instead of 8.
>> >> >> >
>> >> >> > Please be gentle as this is the first time I used git or submitted a
>> >> >> > patch. If this works fine I'll try to submit a patch for a second
>> >> >> > avcodec_find_best_pix_fmt_alt function that'll support more than 64
>> >> >> > formats as input to the function.
>> >> >>
>> >> >> You're welcome. And yes I agree we should replace the function with a
>> >> >> sane variant, for example:
>> >> >>
>> >> >> enum PixelFormat avcodec_find_best_pix_fmt2(int *pix_fmts, int pix_fmts_nb,
>> >> >> enum PixelFormat src_pix_fmt, ...);
>> >> >>
>> >> >> you pass a list of pixel formats (specifying the size, or
>> >> >> alternatively setting the last element to -1), no hardcoded limit on
>> >> >> the number of pixel formats.
>> >> >
>> >> > depending on how its used it might be simpler to have a function
>> >> > comparing 2 pixel formats
>> >> > int is_better_pix_fmt(enum PixelFormat *best, enum PixelFormat try,
>> >> > enum PixelFormat src_pix_fmt, ...);
>> >> >
>> >> > That would avoid having to build the array if it has to be build
>> >> >
>> >> That makes sense, however, the function (patch attached) should have
>> >> more than one destination
>> >> pixel format to choose from. The reason is that we already have a
>> >> avcodec_get_pix_fmt_loss() function
>> >> that could be used to find which pixel format is better as compared to another.
>> >> avcodec_find_best_pix_fmt() is typically used when you have a source
>> >> and multiple destination formats and you
>> >> like to find the best destination format, in that case comparing the
>> >> source to a single dest pixel fmt won't be helpful
>> >> directly because you want to compare multiple destination formats in
>> >> the "context" of the source format. I think the function
>> >> added in the patch solves that.
>> >>
>> >> See in the documentation of the function (in the patch) how this would
>> >> allow to find the best pixel format from a list of formats.
>> >>
>> >>
>> >> In addition, the function allows the user to select which type of loss
>> >> is acceptable to them (loss_ptr) and they aren't locked in to the
>> >> losses as enumerated
>> >> in the loss_mask_order array.
>> >>
>> >> Also, I didn't change the loss_mask_order array that enumerates losses
>> >> in increasing order. However, should that be edited? I'm not sure
>> >> why that order was selected, but I guess now is a good time as any to
>> >> look at that and possibly improve/increase that array? I don't know
>> >> much
>> >> about pix fmts so I don't know if that's already prefect.
>> >>
>> >> Thanks for the application of the previous patch,
>> >> Matt
>> >>
>> >> >
>> >> >>
>> >> >> >
>> >> >> > Thanks,
>> >> >> > Matt
>> >> >>
>> >> >> > From 076c8f936a46ea42cd4242eb4df2db265653d972 Mon Sep 17 00:00:00 2001
>> >> >> > From: Matthew Einhorn <moiein2000 at gmail.com>
>> >> >> > Date: Wed, 17 Aug 2011 01:58:33 -0400
>> >> >> > Subject: [PATCH] Fixes avcodec_find_best_pix_fmt() when there's more than 64
>> >> >> > pixel formats.
>> >> >> >
>> >> >> > This fixed the problem where if there's more than 64 pixel formats defined
>> >> >> > avcodec_find_best_pix_fmt() returns the wrong pixel format.
>> >> >> >
>> >> >> > Signed-off-by: Matthew Einhorn <moiein2000 at gmail.com>
>> >> >> > ---
>> >> >> > libavcodec/avcodec.h | 4 +++-
>> >> >> > libavcodec/imgconvert.c | 2 +-
>> >> >> > 2 files changed, 4 insertions(+), 2 deletions(-)
>> >> >> >
>> >> >> > diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
>> >> >> > index 4f0ed2d..f7d1520 100644
>> >> >> > --- a/libavcodec/avcodec.h
>> >> >> > +++ b/libavcodec/avcodec.h
>> >> >> > @@ -3496,9 +3496,11 @@ int avcodec_get_pix_fmt_loss(enum PixelFormat dst_pix_fmt, enum PixelFormat src_
>> >> >> > * The pixel formats from which it chooses one, are determined by the
>> >> >> > * pix_fmt_mask parameter.
>> >> >> > *
>> >> >> > + * Note, only the first 64 pixel formats will fit in pix_fmt_mask
>> >> >> > + *
>> >> >> > * @code
>> >> >> > * src_pix_fmt = PIX_FMT_YUV420P;
>> >> >> > - * pix_fmt_mask = (1 << PIX_FMT_YUV422P) || (1 << PIX_FMT_RGB24);
>> >> >> > + * pix_fmt_mask = (1 << PIX_FMT_YUV422P) | (1 << PIX_FMT_RGB24);
>> >> >> > * dst_pix_fmt = avcodec_find_best_pix_fmt(pix_fmt_mask, src_pix_fmt, alpha, &loss);
>> >> >> > * @endcode
>> >> >> > *
>> >> >> > diff --git a/libavcodec/imgconvert.c b/libavcodec/imgconvert.c
>> >> >> > index 9efed50..a4197cb 100644
>> >> >> > --- a/libavcodec/imgconvert.c
>> >> >> > +++ b/libavcodec/imgconvert.c
>> >> >> > @@ -439,7 +439,7 @@ static enum PixelFormat avcodec_find_best_pix_fmt1(int64_t pix_fmt_mask,
>> >> >> > /* find exact color match with smallest size */
>> >> >> > dst_pix_fmt = PIX_FMT_NONE;
>> >> >> > min_dist = 0x7fffffff;
>> >> >> > - for(i = 0;i < PIX_FMT_NB; i++) {
>> >> >> > + for(i = 0;i < FFMIN(PIX_FMT_NB, 64); i++) {
>> >> >> > if (pix_fmt_mask & (1ULL << i)) {
>> >> >> > loss = avcodec_get_pix_fmt_loss(i, src_pix_fmt, has_alpha) & loss_mask;
>> >> >> > if (loss == 0) {
>> >> >>
>> >> >> Looks fine to me, I'm going to apply soon if I read no comments (maybe
>> >> >> Michael?).
>> >> >
>> >> > LGTM
>> >> >
>> >> > [...]
>> >> > --
>> >> > Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>> >> >
>> >> > Observe your enemies, for they first find out your faults. -- Antisthenes
>> >> >
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>> >> > Version: GnuPG v1.4.10 (GNU/Linux)
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>> >> >
>> >> > _______________________________________________
>> >> > ffmpeg-devel mailing list
>> >> > ffmpeg-devel at ffmpeg.org
>> >> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>> >> >
>> >> >
>> >
>> >> avcodec.h | 34 ++++++++++++++++++++++++++++++++++
>> >> imgconvert.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>> >> 2 files changed, 80 insertions(+)
>> >> a2185b7288f78de01eaf39b89f5de1d313643607 0001-Adds-a-new-pix-fmt-function-that-selects-the-best-de.patch
>> >> From a873e791be7802b110ac44e279b904d28e2e2fb4 Mon Sep 17 00:00:00 2001
>> >> From: Matthew Einhorn <moiein2000 at gmail.com>
>> >> Date: Wed, 17 Aug 2011 20:14:54 -0400
>> >> Subject: [PATCH] Adds a new pix fmt function that selects the best dest fmt
>> >> from among 2 formats to convert to, given a certain src
>> >> format.
>> >>
>> >> Similar to avcodec_find_best_pix_fmt(), but instead only compares two destination
>> >> pix fmts and selects one of these fmts as the best dest format when converting from
>> >> a given source format. Also, as opposed to avcodec_find_best_pix_fmt() which supports
>> >> only the first 64 defined pixel formats, this supports as input any of the defined
>> >> pixel formats.
>> >>
>> >> Signed-off-by: Matthew Einhorn <moiein2000 at gmail.com>
>> >> ---
>> >> libavcodec/avcodec.h | 34 ++++++++++++++++++++++++++++++++++
>> >> libavcodec/imgconvert.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>> >> 2 files changed, 80 insertions(+), 0 deletions(-)
>> >
>> > The old function should be replaced by the new and the old then
>> > implemented by using the new
>>
>> Should I implement new and re-implement old in one patch or in two patches?
>
> both in one patch
>
>
>>
>> Also, the old function makes use of an internal
>> avcodec_find_best_pix_fmt1() function which is used "only" by the old
>> function, can I remove that?
>
> yes but that should be a seperate patch
>
>
>>
>> Finally, the new function allows the input of PIX_FMT_NONE as a
>> destination format because it would simplify the use of it (if "one"
>> of the dest pix fmts can be -1) because you'd have to do less error
>> checking. However, to do that avcodec_get_pix_fmt_loss() also needs to
>> support the "dst_pix_fmt" parameter to be PIX_FMT_NONE (otherwise I
>> need to check for it in the new function). Would it be appropriate to
>> patch avcodec_get_pix_fmt_loss() to include a line of code at the
>> start where if the dest format is -1 it returns the maximum loss or
>> should it stay as undefined behavior (since arrays then get indexed by
>> -1)?
>
> yes, of course
>
All three patches attached
Thanks,
Matt
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