[FFmpeg-devel] [PATCH] libavcodec/dnxhdenc: remove setting the codec_tag

[Mark Reid]

On Fri, Aug 5, 2016 at 4:28 AM, Michael Niedermayer
<michael at niedermayer.cc> wrote:
> On Fri, Aug 05, 2016 at 12:58:10PM +0200, Paul B Mahol wrote:
>> On 8/5/16, Michael Niedermayer <michael at niedermayer.cc> wrote:
>> > On Wed, Aug 03, 2016 at 02:31:04PM -0700, Mark Reid wrote:
>> >> setting the codec_tag no longer needed by movenc
>> >> it uses the dnxhr profile instead
>> >> ---
>> >>  libavcodec/dnxhdenc.c | 3 ---
>> >>  1 file changed, 3 deletions(-)
>> >>
>> >> diff --git a/libavcodec/dnxhdenc.c b/libavcodec/dnxhdenc.c
>> >> index b0ee8a2..cbf4cd5 100644
>> >> --- a/libavcodec/dnxhdenc.c
>> >> +++ b/libavcodec/dnxhdenc.c
>> >> @@ -341,9 +341,6 @@ static av_cold int dnxhd_encode_init(AVCodecContext
>> >> *avctx)
>> >>      }
>> >>      av_log(avctx, AV_LOG_DEBUG, "cid %d\n", ctx->cid);
>> >>
>> >> -    if (ctx->cid >= 1270 && ctx->cid <= 1274)
>> >> -        avctx->codec_tag = MKTAG('A','V','d','h');
>> >
>> > does this not break older libavformat ?
>> > newer libavcodec could be used with older libavformat
>>

In that case I can just leave it as is and drop the patch. It was bit
unclear as to whether the encoder was allowed to set codec_tag and
thats why I was trying to clean it up.

>> Are you serious? That kind of scenario is bad idea and it never worked
>> and was never tested.
>
> its tested by the users of binary packages in linux distros
> debian and ubuntu being examples
>
> each lib has major, minor and micro versions
>
>     MAJOR version when you make incompatible API changes,
>     MINOR version when you add functionality in a backwards-compatible manner, and
>     PATCH version when you make backwards-compatible bug fixes.
> (taken from http://semver.org/)
>
> so if minor is bumped in libavcodec then it has a new feature and
> libavformat at that point and later might need that feature and
> thus there will be a matching dependancy libavformat->libavcodec >= x.y
>
> but if libavformat bumps minor, libavcodec does not depend on
> libavcodec thus there wont be a dependancy.
>
> any lib with larger minor version must work as a drop in for older
> versions of same major version
>
> you can also see this in the actual dependancies on ubuntu for example:
>
> apt-cache show libavformat-ffmpeg56 libavcodec-ffmpeg56 | grep Depends
>
> Depends: libavcodec-ffmpeg56 (>= 7:2.7) | libavcodec-ffmpeg-extra56 (>= 7:2.7), libavutil-ffmpeg54 (>= 7:2.8), libbluray1 (>= 1:0.2.2), libbz2-1.0, libc6 (>= 2.14), libgme0 (>= 0.5.5), libgnutls30 (>= 3.4.2), libmodplug1 (>= 1:0.8.8.5), librtmp1 (>= 2.3), libssh-gcrypt-4 (>= 0.4.2), zlib1g (>= 1:1.2.0.2)
>
> Depends: libavutil-ffmpeg54 (>= 7:2.6), libc6 (>= 2.14), libcrystalhd3
> (>= 1:0.0~git20110715.fdd2f19), libgsm1 (>= 1.0.13), liblzma5 (>= 5.1.1alpha+20120614), libmp3lame0, libopenjpeg5 (>= 1.3+dfsg), libopus0 (>= 1.1), libschroedinger-1.0-0 (>= 1.0.0), libshine3 (>= 3.1.0), libsnappy1v5, libspeex1 (>= 1.2~beta3-1), libswresample-ffmpeg1 (>= 7:2.4), libtheora0 (>= 1.0), libtwolame0, libva1 (>= 1.0.3), libvorbis0a (>= 1.1.2), libvorbisenc2 (>= 1.1.2), libvpx3 (>= 1.5.0), libwavpack1 (>= 4.40.0), libwebp5 (>= 0.4.3), libx264-148, libx265-79 (>= 1.9), libxvidcore4 (>= 1.2.2), libzvbi0 (>= 0.2.35), zlib1g (>= 1:1.2.0)
>

as this would be a small change in behaviour and not a binary
incompatibility would this then be a MINOR bump?

> [...]
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> The educated differ from the uneducated as much as the living from the
> dead. -- Aristotle
>
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