[FFmpeg-devel] [PATCH] avformat/wavdec: allow to change max size of single demuxed packet

[Paul B Mahol]

On 8/28/20, Andreas Rheinhardt <andreas.rheinhardt at gmail.com> wrote:
> Paul B Mahol:
>> On 8/28/20, Andreas Rheinhardt <andreas.rheinhardt at gmail.com> wrote:
>>> Paul B Mahol:
>>>> Can make demuxing much faster, expecially for files with
>>>> huge number of channels.
>>>>
>>>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>>>> ---
>>>>  libavformat/wavdec.c | 21 ++++++++++++++++++---
>>>>  1 file changed, 18 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/libavformat/wavdec.c b/libavformat/wavdec.c
>>>> index e1b2115434..5b3c481421 100644
>>>> --- a/libavformat/wavdec.c
>>>> +++ b/libavformat/wavdec.c
>>>> @@ -56,6 +56,7 @@ typedef struct WAVDemuxContext {
>>>>      int smv_eof;
>>>>      int audio_eof;
>>>>      int ignore_length;
>>>> +    int max_size;
>>>>      int spdif;
>>>>      int smv_cur_pt;
>>>>      int smv_given_first;
>>>> @@ -628,8 +629,6 @@ static int64_t find_guid(AVIOContext *pb, const
>>>> uint8_t guid1[16])
>>>>      return AVERROR_EOF;
>>>>  }
>>>>
>>>> -#define MAX_SIZE 4096
>>>> -
>>>>  static int wav_read_packet(AVFormatContext *s, AVPacket *pkt)
>>>>  {
>>>>      int ret, size;
>>>> @@ -706,7 +705,7 @@ smv_out:
>>>>          wav->data_end = avio_tell(s->pb) + left;
>>>>      }
>>>>
>>>> -    size = MAX_SIZE;
>>>> +    size = wav->max_size;
>>>>      if (st->codecpar->block_align > 1) {
>>>>          if (size < st->codecpar->block_align)
>>>>              size = st->codecpar->block_align;
>>>> @@ -759,6 +758,7 @@ static int wav_read_seek(AVFormatContext *s,
>>>>  #define DEC AV_OPT_FLAG_DECODING_PARAM
>>>>  static const AVOption demux_options[] = {
>>>>      { "ignore_length", "Ignore length", OFFSET(ignore_length),
>>>> AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, DEC },
>>>> +    { "max_size",      "max size of single packet", OFFSET(max_size),
>>>> AV_OPT_TYPE_INT, { .i64 = 4096 }, 1024, 1 << 22, DEC },
>>>>      { NULL },
>>>>  };
>>>>
>>>> @@ -906,6 +906,20 @@ static int w64_read_header(AVFormatContext *s)
>>>>      return 0;
>>>>  }
>>>>
>>>> +#define OFFSET(x) offsetof(WAVDemuxContext, x)
>>>> +#define DEC AV_OPT_FLAG_DECODING_PARAM
>>>> +static const AVOption w64_demux_options[] = {
>>>> +    { "max_size", "max size of single packet", OFFSET(max_size),
>>>> AV_OPT_TYPE_INT, { .i64 = 4096 }, 1024, 1 << 22, DEC },
>>>> +    { NULL },
>>>
>>> The ',' is unnecessary: Nothing will ever be added after the sentinel.
>>>
>>>> +};
>>>
>>> You can use &demux_options[1] instead of w64_demux_options (but add a
>>> comment for this).
>>
>> How the comment should look like?
>>
>
> I thought of a comment for demux_options like "Hint: The options are
> partially shared with the Wave64 demuxer."

More like Warning instead of Hint.
So some other developer does not add option that does not make sense for w64.

>
>>>
>>>> +
>>>> +static const AVClass w64_demuxer_class = {
>>>> +    .class_name = "W64 demuxer",
>>>> +    .item_name  = av_default_item_name,
>>>> +    .option     = w64_demux_options,
>>>> +    .version    = LIBAVUTIL_VERSION_INT,
>>>> +};
>>>> +
>>>>  AVInputFormat ff_w64_demuxer = {
>>>>      .name           = "w64",
>>>>      .long_name      = NULL_IF_CONFIG_SMALL("Sony Wave64"),
>>>> @@ -916,5 +930,6 @@ AVInputFormat ff_w64_demuxer = {
>>>>      .read_seek      = wav_read_seek,
>>>>      .flags          = AVFMT_GENERIC_INDEX,
>>>>      .codec_tag      = (const AVCodecTag * const []) {
>>>> ff_codec_wav_tags,
>>>> 0 },
>>>> +    .priv_class     = &w64_demuxer_class,
>>>>  };
>>>>  #endif /* CONFIG_W64_DEMUXER */
>>>>
>>>
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