[FFmpeg-devel] [PATCH 2/2] avformat/hnm: Only keep and parse what is needed later

[Paul B Mahol]

ok if fate passed and it is covered.

On 3/21/20, Andreas Rheinhardt <andreas.rheinhardt at gmail.com> wrote:
> The hnm demuxer's context struct contained lots of fields that are
> write-only variables or that are not used outside of parsing the header
> and that can therefore be replaced by local variables of hnm_read_header().
> This commit removes all of these from the context; the second type has
> been replaced by local variables.
>
> An AVPacket (that was initialized when reading the header and for which
> dead code to unreference it existed in hnm_read_close()) is among the
> removed things. Removing it allowed to remove hnm_read_close()
> altogether and also removes another instance of usage of sizeof(AVPacket).
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
>  libavformat/hnm.c | 63 +++++++++--------------------------------------
>  1 file changed, 12 insertions(+), 51 deletions(-)
>
> diff --git a/libavformat/hnm.c b/libavformat/hnm.c
> index 31221553a4..f06add5cf8 100644
> --- a/libavformat/hnm.c
> +++ b/libavformat/hnm.c
> @@ -37,19 +37,9 @@
>  #define HNM4_CHUNK_ID_SD 17491
>
>  typedef struct Hnm4DemuxContext {
> -    uint8_t version;
> -    uint16_t width;
> -    uint16_t height;
> -    uint32_t filesize;
>      uint32_t frames;
> -    uint32_t taboffset;
> -    uint16_t bits;
> -    uint16_t channels;
> -    uint32_t framesize;
>      uint32_t currentframe;
> -    int64_t pts;
>      uint32_t superchunk_remaining;
> -    AVPacket vpkt;
>  } Hnm4DemuxContext;
>
>  static int hnm_probe(const AVProbeData *p)
> @@ -69,55 +59,37 @@ static int hnm_read_header(AVFormatContext *s)
>  {
>      Hnm4DemuxContext *hnm = s->priv_data;
>      AVIOContext *pb = s->pb;
> +    unsigned width, height;
>      AVStream *vst;
>      int ret;
>
> -    /* default context members */
> -    hnm->pts = 0;
> -    av_init_packet(&hnm->vpkt);
> -    hnm->vpkt.data = NULL;
> -    hnm->vpkt.size = 0;
> -
> -    hnm->superchunk_remaining = 0;
> -
>      avio_skip(pb, 8);
> -    hnm->width     = avio_rl16(pb);
> -    hnm->height    = avio_rl16(pb);
> -    hnm->filesize  = avio_rl32(pb);
> +    width          = avio_rl16(pb);
> +    height         = avio_rl16(pb);
> +    avio_rl32(pb); // filesize
>      hnm->frames    = avio_rl32(pb);
> -    hnm->taboffset = avio_rl32(pb);
> -    hnm->bits      = avio_rl16(pb);
> -    hnm->channels  = avio_rl16(pb);
> -    hnm->framesize = avio_rl32(pb);
> -    avio_skip(pb, 32);
> +    avio_skip(pb, 44);
>
> -    hnm->currentframe = 0;
> -
> -    if (hnm->width  < 256 || hnm->width  > 640 ||
> -        hnm->height < 150 || hnm->height > 480) {
> +    if (width  < 256 || width  > 640 ||
> +        height < 150 || height > 480) {
>          av_log(s, AV_LOG_ERROR,
> -               "invalid resolution: %ux%u\n", hnm->width, hnm->height);
> +               "invalid resolution: %ux%u\n", width, height);
>          return AVERROR_INVALIDDATA;
>      }
>
> -    // TODO: find a better way to detect HNM4A
> -    if (hnm->width == 640)
> -        hnm->version = 0x4a;
> -    else
> -        hnm->version = 0x40;
> -
>      if (!(vst = avformat_new_stream(s, NULL)))
>          return AVERROR(ENOMEM);
>
>      vst->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
>      vst->codecpar->codec_id   = AV_CODEC_ID_HNM4_VIDEO;
>      vst->codecpar->codec_tag  = 0;
> -    vst->codecpar->width      = hnm->width;
> -    vst->codecpar->height     = hnm->height;
> +    vst->codecpar->width      = width;
> +    vst->codecpar->height     = height;
>      if ((ret = ff_alloc_extradata(vst->codecpar, 1)) < 0)
>          return ret;
>
> -    vst->codecpar->extradata[0] = hnm->version;
> +    // TODO: find a better way to detect HNM4A
> +    vst->codecpar->extradata[0] = width == 640 ? 0x4a : 0x40;
>
>      vst->start_time = 0;
>
> @@ -186,16 +158,6 @@ static int hnm_read_packet(AVFormatContext *s, AVPacket
> *pkt)
>      return ret;
>  }
>
> -static int hnm_read_close(AVFormatContext *s)
> -{
> -    Hnm4DemuxContext *hnm = s->priv_data;
> -
> -    if (hnm->vpkt.size > 0)
> -        av_packet_unref(&hnm->vpkt);
> -
> -    return 0;
> -}
> -
>  AVInputFormat ff_hnm_demuxer = {
>      .name           = "hnm",
>      .long_name      = NULL_IF_CONFIG_SMALL("Cryo HNM v4"),
> @@ -203,6 +165,5 @@ AVInputFormat ff_hnm_demuxer = {
>      .read_probe     = hnm_probe,
>      .read_header    = hnm_read_header,
>      .read_packet    = hnm_read_packet,
> -    .read_close     = hnm_read_close,
>      .flags          = AVFMT_NO_BYTE_SEEK | AVFMT_NOGENSEARCH |
> AVFMT_NOBINSEARCH
>  };
> --
> 2.20.1
>
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