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

[Paul B Mahol]

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.