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

[Paul B Mahol]

On 8/28/20, Paul B Mahol <onemda at gmail.com> wrote:
> 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.

Problem is demux_options are under ifdef so can not be shared as is.
What about using macro to define max_size option or just keep it as in
this patch.

>
>>
>>>>
>>>>> +
>>>>> +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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>>
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>