[FFmpeg-devel] [FFmpeg-cvslog] avcodec/gif: enable encoding single gif image per frame

[Paul B Mahol]

On 12/15/18, Paul B Mahol <onemda at gmail.com> wrote:
> On 12/15/18, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>> 2018-12-13 19:32 GMT+01:00, Paul B Mahol <git at videolan.org>:
>>> ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Wed Dec 12
>>> 13:19:33 2018 +0100| [bb0984cc29e93e56506722fe0ce5c6d43b6d4326] |
>>> committer:
>>> Paul B Mahol
>>>
>>> avcodec/gif: enable encoding single gif image per frame
>>>
>>> Unbreaks gif image2 muxer.
>>>
>>>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=bb0984cc29e93e56506722fe0ce5c6d43b6d4326
>>> ---
>>>
>>>  libavcodec/gif.c | 20 ++++++++++++++------
>>>  1 file changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/libavcodec/gif.c b/libavcodec/gif.c
>>> index 408b7534da..67fc5a1bda 100644
>>> --- a/libavcodec/gif.c
>>> +++ b/libavcodec/gif.c
>>> @@ -51,6 +51,7 @@ typedef struct GIFContext {
>>>      int is_first_frame;
>>>      AVFrame *last_frame;
>>>      int flags;
>>> +    int image;
>>>      uint32_t palette[AVPALETTE_COUNT];  ///< local reference palette
>>> for
>>> !pal8
>>>      int palette_loaded;
>>>      int transparent_index;
>>> @@ -422,6 +423,9 @@ static int gif_encode_frame(AVCodecContext *avctx,
>>> AVPacket *pkt,
>>>      outbuf_ptr = pkt->data;
>>>      end        = pkt->data + pkt->size;
>>>
>>> +    if (s->image)
>>> +        s->is_first_frame = 1;
>>> +
>>>      if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {
>>>          palette = (uint32_t*)pict->data[1];
>>>
>>> @@ -436,19 +440,22 @@ static int gif_encode_frame(AVCodecContext *avctx,
>>> AVPacket *pkt,
>>>
>>>      gif_image_write_image(avctx, &outbuf_ptr, end, palette,
>>>                            pict->data[0], pict->linesize[0], pkt);
>>> -    if (!s->last_frame) {
>>> +    if (!s->last_frame && !s->image) {
>>>          s->last_frame = av_frame_alloc();
>>>          if (!s->last_frame)
>>>              return AVERROR(ENOMEM);
>>>      }
>>>
>>> -    av_frame_unref(s->last_frame);
>>> -    ret = av_frame_ref(s->last_frame, (AVFrame*)pict);
>>> -    if (ret < 0)
>>> -        return ret;
>>> +    if (!s->image) {
>>> +        av_frame_unref(s->last_frame);
>>> +        ret = av_frame_ref(s->last_frame, (AVFrame*)pict);
>>> +        if (ret < 0)
>>> +            return ret;
>>> +    }
>>>
>>>      pkt->size   = outbuf_ptr - pkt->data;
>>> -    pkt->flags |= AV_PKT_FLAG_KEY;
>>> +    if (s->is_first_frame)
>>> +        pkt->flags |= AV_PKT_FLAG_KEY;
>>>      *got_packet = 1;
>>>
>>>      return 0;
>>> @@ -472,6 +479,7 @@ static const AVOption gif_options[] = {
>>>      { "gifflags", "set GIF flags", OFFSET(flags), AV_OPT_TYPE_FLAGS,
>>> {.i64
>>> = GF_OFFSETTING|GF_TRANSDIFF}, 0, INT_MAX, FLAGS, "flags" },
>>>          { "offsetting", "enable picture offsetting", 0,
>>> AV_OPT_TYPE_CONST,
>>> {.i64=GF_OFFSETTING}, INT_MIN, INT_MAX, FLAGS, "flags" },
>>>          { "transdiff", "enable transparency detection between frames",
>>> 0,
>>> AV_OPT_TYPE_CONST, {.i64=GF_TRANSDIFF}, INT_MIN, INT_MAX, FLAGS, "flags"
>>> },
>>> +    { "gifimage", "enable encoding only images per frame",
>>> OFFSET(image),
>>> AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS, "flags" },
>>
>> Would it not be possible to detect in the flush function that only one
>> frame
>> was encoded and make the flag unnecessary?
>
> Unfortunately not, gif encoder is not reset anywhere and so
> frame_number is never set back to 0.
>

I could use par->codec_tag for this 'GIFI' for images, image2 muxer
would set this, and encoder could check it, but this is far from
perfect solution.