[FFmpeg-devel] [PATCH 2/4] API: add AV_PKT_DATA_S12M_TIMECODE to AVPacketSideDataType

lance.lmwang at gmail.com lance.lmwang at gmail.com
Mon Jun 29 17:00:57 EEST 2020


On Mon, Jun 29, 2020 at 03:52:00PM +0200, Andreas Rheinhardt wrote:
> lance.lmwang at gmail.com:
> > On Mon, Jun 29, 2020 at 02:06:49PM +0200, Andreas Rheinhardt wrote:
> >> lance.lmwang at gmail.com:
> >>> On Mon, Jun 29, 2020 at 04:53:21AM +0200, Andreas Rheinhardt wrote:
> >>>> lance.lmwang at gmail.com:
> >>>>> From: Limin Wang <lance.lmwang at gmail.com>
> >>>>>
> >>>>> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> >>>>> ---
> >>>>>  doc/APIchanges        |  3 +++
> >>>>>  libavcodec/avpacket.c |  1 +
> >>>>>  libavcodec/decode.c   |  1 +
> >>>>>  libavcodec/packet.h   |  8 ++++++++
> >>>>>  libavcodec/version.h  |  2 +-
> >>>>>  libavformat/dump.c    | 22 ++++++++++++++++++++++
> >>>>>  6 files changed, 36 insertions(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/doc/APIchanges b/doc/APIchanges
> >>>>> index 1d6cc36..7cad7fa 100644
> >>>>> --- a/doc/APIchanges
> >>>>> +++ b/doc/APIchanges
> >>>>> @@ -15,6 +15,9 @@ libavutil:     2017-10-21
> >>>>>  
> >>>>>  API changes, most recent first:
> >>>>>  
> >>>>> +2020-06-xx - xxxxxxxxxx - lavc 58.94.100 - packet.h
> >>>>> +  Add AV_PKT_DATA_S12M_TIMECODE.
> >>>>> +
> >>>>>  2020-06-12 - b09fb030c1 - lavu 56.55.100 - pixdesc.h
> >>>>>    Add AV_PIX_FMT_X2RGB10.
> >>>>>  
> >>>>> diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
> >>>>> index dce26cb..a4316a7 100644
> >>>>> --- a/libavcodec/avpacket.c
> >>>>> +++ b/libavcodec/avpacket.c
> >>>>> @@ -400,6 +400,7 @@ const char *av_packet_side_data_name(enum AVPacketSideDataType type)
> >>>>>      case AV_PKT_DATA_PRFT:                       return "Producer Reference Time";
> >>>>>      case AV_PKT_DATA_ICC_PROFILE:                return "ICC Profile";
> >>>>>      case AV_PKT_DATA_DOVI_CONF:                  return "DOVI configuration record";
> >>>>> +    case AV_PKT_DATA_S12M_TIMECODE:              return "SMPTE 12-1 timecode";
> >>>>>      }
> >>>>>      return NULL;
> >>>>>  }
> >>>>> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> >>>>> index a4e50c0..a2bf0cc 100644
> >>>>> --- a/libavcodec/decode.c
> >>>>> +++ b/libavcodec/decode.c
> >>>>> @@ -1699,6 +1699,7 @@ int ff_decode_frame_props(AVCodecContext *avctx, AVFrame *frame)
> >>>>>          { AV_PKT_DATA_CONTENT_LIGHT_LEVEL,        AV_FRAME_DATA_CONTENT_LIGHT_LEVEL },
> >>>>>          { AV_PKT_DATA_A53_CC,                     AV_FRAME_DATA_A53_CC },
> >>>>>          { AV_PKT_DATA_ICC_PROFILE,                AV_FRAME_DATA_ICC_PROFILE },
> >>>>> +        { AV_PKT_DATA_S12M_TIMECODE,              AV_FRAME_DATA_S12M_TIMECODE },
> >>>>>      };
> >>>>>  
> >>>>>      if (pkt) {
> >>>>> diff --git a/libavcodec/packet.h b/libavcodec/packet.h
> >>>>> index 41485f4..72cb4f7 100644
> >>>>> --- a/libavcodec/packet.h
> >>>>> +++ b/libavcodec/packet.h
> >>>>> @@ -283,6 +283,14 @@ enum AVPacketSideDataType {
> >>>>>      AV_PKT_DATA_DOVI_CONF,
> >>>>>  
> >>>>>      /**
> >>>>> +     * Timecode which conforms to SMPTE ST 12-1. The data is an array of 4 uint32_t
> >>>>> +     * where the first uint32_t describes how many (1-3) of the other timecodes are used.
> >>>>> +     * The timecode format is described in the av_timecode_get_smpte_from_framenum()
> >>>>> +     * function in libavutil/timecode.c.
> >>>>
> >>>> The format is documented in a C source file, not a public header? Sure
> >>>> about that?
> >>>
> >>> For AV_PKT_DATA_S12M_TIMECODE use the same format with AV_FRAME_DATA_S12M_TIMECODE, so I copy the
> >>> comments for AV_FRAME_DATA_S12M_TIMECODE, it's not my comments for it. I think the format is described
> >>> in "SMPTE ST 12-2:2014" standard document, but it's not free for download.
> >>>
> >>
> >> It's SMPTE ST 12-1:2014 and this standard is currently (until 21 July)
> >> available for free [1] due to Corona.
> > 
> > oh, it's good to hear it's free due to Corona. I haven't notice it's online.
> > 
> >>
> >>> What's your suggestion to change?
> >>>
> >>
> >> The best is probably to incorporate the documentation of the format into
> >> the documentation of av_timecode_get_smpte_from_framenum.
> > OK, I'll remove the comments for the timecode format.
> >>
> >>>>
> >>>>> +     */
> >>>>> +    AV_PKT_DATA_S12M_TIMECODE,
> >>>>> +
> >>>>> +    /**
> >>>>>       * The number of side data types.
> >>>>>       * This is not part of the public API/ABI in the sense that it may
> >>>>>       * change when new side data types are added.
> >>>>> diff --git a/libavcodec/version.h b/libavcodec/version.h
> >>>>> index 0359302..482cc6d 100644
> >>>>> --- a/libavcodec/version.h
> >>>>> +++ b/libavcodec/version.h
> >>>>> @@ -28,7 +28,7 @@
> >>>>>  #include "libavutil/version.h"
> >>>>>  
> >>>>>  #define LIBAVCODEC_VERSION_MAJOR  58
> >>>>> -#define LIBAVCODEC_VERSION_MINOR  93
> >>>>> +#define LIBAVCODEC_VERSION_MINOR  94
> >>>>>  #define LIBAVCODEC_VERSION_MICRO 100
> >>>>>  
> >>>>>  #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
> >>>>> diff --git a/libavformat/dump.c b/libavformat/dump.c
> >>>>> index 117c681..c5f0bd6 100644
> >>>>> --- a/libavformat/dump.c
> >>>>> +++ b/libavformat/dump.c
> >>>>> @@ -34,6 +34,7 @@
> >>>>>  #include "libavutil/replaygain.h"
> >>>>>  #include "libavutil/spherical.h"
> >>>>>  #include "libavutil/stereo3d.h"
> >>>>> +#include "libavutil/timecode.h"
> >>>>>  
> >>>>>  #include "avformat.h"
> >>>>>  
> >>>>> @@ -402,6 +403,23 @@ static void dump_dovi_conf(void *ctx, AVPacketSideData* sd)
> >>>>>             dovi->dv_bl_signal_compatibility_id);
> >>>>>  }
> >>>>>  
> >>>>> +static void dump_s12m_timecode(void *ctx, AVPacketSideData* sd)
> >>>>> +{
> >>>>> +    uint32_t *tc = (uint32_t*)sd->data;
> >>>>> +    int m = tc[0] & 3;
> >>>>> +
> >>>>> +    if (sd->size != sizeof(uint32_t) * 4) {
> >>
> >> You already dereferenced tc before this check which might crash if the
> >> size is actually < sizeof(uint32_t). And why do you only look at the
> >> lowest two bits of m? Is this designed with future extensions of the
> >> timecode in mind? But even then one can't simply use the upper 30 bits
> >> to store something else, because that has not been documented.
> >> (Moreover, if one allowed extensions, one should allow sd->size to be >=
> >> sizeof(uint32_t) * 4.)
> > 
> > It's from the comments for the side data, it used to avoid index overflow,
> > for the array is 4. I'll fix to get the m after the checking.
> 
> I know it is to ensure that you don't overread. I'd simply consider it
> invalid data if the count were > 3.

I agree, I'll update to report invalid data if count > 3. To keep consistent,
I'll change the vf_showinfo.c dump to keep the code consistent later.

> 
> > 
> > comments:
> > where the first uint32_t describes how many (1-3) of the other timecodes are used
> > 
> > I think it's for the timecode SEI define 2bits for the count of used timecomes,
> > it's not related to SMPTE ST 12-1. vf_showinfo.c have dump AV_FRAME_DATA_S12M_TIMECODE,
> > I'm following it as format is same, but change m to & 3 for I think it's more simple.
> > 
> > 
> >>
> >>>>> +        av_log(ctx, AV_LOG_ERROR, "invalid data");
> >>>>> +        return;
> >>>>> +    }
> >>>>> +
> >>>>> +    for (int j = 1; j <= m; j++) {
> >>>>> +        char tcbuf[AV_TIMECODE_STR_SIZE];
> >>>>> +        av_timecode_make_smpte_tc_string(tcbuf, tc[j], 0);
> >>>>> +        av_log(ctx, AV_LOG_INFO, "timecode - %s%s", tcbuf, j != m ? ", " : "");
> >>>>> +    }
> >>>>> +}
> >>>>> +
> >>
> >> - Andreas
> >>
> >> [1]: https://www.smpte.org/free-standards-and-publications
> >> _______________________________________________
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> >>
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> > 
> 
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-- 
Thanks,
Limin Wang


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