Re: [FFmpeg-devel] [PATCH] avformat/framecrcenc: List types and checksums for for side data

[Michael Niedermayer <michael@niedermayer.cc>]

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On Sun, May 18, 2025 at 11:43:14AM -0300, James Almer wrote:
> On 5/18/2025 9:25 AM, Michael Niedermayer wrote:
> > This allows detecting changes and regressions in side data related code, same as what
> > framecrc does for before already for packet data itself.
> > 
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >   libavformat/framecrcenc.c                   |  116 +-
> >   tests/ref/fate/autorotate                   |    2 +-
> >   tests/ref/fate/cover-art-mp3-id3v2-remux    |    2 +-
> >   tests/ref/fate/ffmpeg-bsf-input             |   10 +-
> >   tests/ref/fate/ffmpeg-spec-disposition      |    2 +-
> >   tests/ref/fate/force_key_frames-source      |  784 ++++++------
> >   tests/ref/fate/force_key_frames-source-drop |   34 +-
> >   tests/ref/fate/force_key_frames-source-dup  | 1224 +++++++++----------
> >   tests/ref/fate/gapless-mp3                  |    6 +-
> >   tests/ref/fate/h264_redundant_pps-side_data |    2 +-
> >   tests/ref/fate/id3v2-priv-remux             |    2 +-
> >   tests/ref/fate/matroska-hdr10-plus-remux    |    2 +-
> >   tests/ref/fate/matroska-ogg-opus-remux      |    2 +-
> >   tests/ref/fate/matroska-opus-remux          |    2 +-
> >   tests/ref/fate/matroska-vp8-alpha-remux     |   14 +-
> >   tests/ref/fate/mov-cover-image              |    2 +-
> >   tests/ref/fate/segment-mp4-to-ts            |  250 ++--
> >   tests/ref/fate/shortest                     |  100 +-
> >   tests/ref/fate/webm-hdr10-plus-remux        |    2 +-
> >   tests/ref/fate/webm-webvtt-remux            |   24 +-
> >   20 files changed, 1346 insertions(+), 1236 deletions(-)
> > 
> > diff --git a/libavformat/framecrcenc.c b/libavformat/framecrcenc.c
> > index 2ba20f3aab4..96c2a82eb2a 100644
> > --- a/libavformat/framecrcenc.c
> > +++ b/libavformat/framecrcenc.c
> > @@ -21,8 +21,11 @@
> >   #include <inttypes.h>
> > +#include "config.h"
> >   #include "libavutil/adler32.h"
> >   #include "libavutil/avstring.h"
> > +#include "libavutil/intreadwrite.h"
> > +#include "libavutil/hdr_dynamic_metadata.h"
> >   #include "libavcodec/codec_id.h"
> >   #include "libavcodec/codec_par.h"
> > @@ -48,6 +51,20 @@ static int framecrc_write_header(struct AVFormatContext *s)
> >       return ff_framehash_write_header(s);
> >   }
> > +static av_unused void inline bswap(char *buf, int offset, int size)
> > +{
> > +    if (size == 8) {
> > +        uint64_t val = AV_RN64(buf + offset);
> > +        AV_WN64(buf + offset, av_bswap64(val));
> > +    } else if (size == 4) {
> > +        uint32_t val = AV_RN32(buf + offset);
> > +        AV_WN32(buf + offset, av_bswap32(val));
> > +    } else if (size == 2) {
> > +        uint16_t val = AV_RN16(buf + offset);
> > +        AV_WN16(buf + offset, av_bswap16(val));
> > +    }
> > +}
> > +
> >   static int framecrc_write_packet(struct AVFormatContext *s, AVPacket *pkt)
> >   {
> >       uint32_t crc = av_adler32_update(0, pkt->data, pkt->size);
> > @@ -58,11 +75,104 @@ static int framecrc_write_packet(struct AVFormatContext *s, AVPacket *pkt)
> >       if (pkt->flags != AV_PKT_FLAG_KEY)
> >           av_strlcatf(buf, sizeof(buf), ", F=0x%0X", pkt->flags);
> >       if (pkt->side_data_elems) {
> > +        int i;
> >           av_strlcatf(buf, sizeof(buf), ", S=%d", pkt->side_data_elems);
> > -        for (int i = 0; i < pkt->side_data_elems; i++) {
> > -            av_strlcatf(buf, sizeof(buf), ", %8"SIZE_SPECIFIER,
> > -                        pkt->side_data[i].size);
> > +        for (i=0; i<pkt->side_data_elems; i++) {
> > +            const AVPacketSideData *const sd = &pkt->side_data[i];
> > +            const uint8_t *data = sd->data;
> > +            uint32_t side_data_crc = 0;
> > +
> > +            switch (sd->type) {
> 
> Wont this potentially introduce extra work for when we add new types?

no, it will be less work

because maintaining this in a seperate branch is the identical work
but in addition its also the extra work due to the seperate branch.
and it adds complexity if one wants to bisect.

Every hour i have to spend maintaining this or anything
else in a seperate branch is an hour less i spend on the ffmpeg core
repository.

Maybe I should write this in a more formal way to show it

Developer_t = Michael_t + James_t + ...

Case 1:
    Michael_t contains SD_t = time needed to maintain sidedata testing
    Michael_t contains SB_t = time needed to maintain a seperate branch with side data testing and checksums

Case 2:
    Developer_t contains SD_t = time needed to maintain sidedata testing

In both cases Developer_t contains SD_t so it cancels out
but in case 1, Developer_t also contains SB_t that is the time needed to
maintain sidedata checksums in a seperate branch.
So with a seperate branch the developers will have less time remainining

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

During times of universal deceit, telling the truth becomes a
revolutionary act. -- George Orwell

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