[FFmpeg-devel] [PATCH] avformat/mxfenc: support XAVC long gop

[Paul B Mahol]

On 5/12/19, Baptiste Coudurier <baptiste.coudurier at gmail.com> wrote:
> Hi Tomas
>
>> On May 12, 2019, at 6:47 AM, Tomas Härdin <tjoppen at acc.umu.se> wrote:
>>
>> fre 2019-05-10 klockan 08:50 -0700 skrev Baptiste Coudurier:
>>> +static inline int get_ue_golomb(GetBitContext *gb) {
>>> +    int i, v;
>>> +    for (i = 0; i < 32 && !get_bits1(gb); i++)
>>> +        ;
>>> +    for (v = 1; i--;)
>>> +        v = (v << 1) | get_bits1(gb);
>>
>> Isn't there already a function to get variable number of bits?
>
> get_bits doesn’t work for n == 0

There is get_bitsz. Or I misunderstood?

>
>>>
>>> +
>>> +    sps->profile_idc = get_bits(&gb, 8);
>>> +    sps->constraint_set_flags |= get_bits1(&gb) << 0; //
>>> constraint_set0_flag
>>> +    sps->constraint_set_flags |= get_bits1(&gb) << 1; //
>>> constraint_set1_flag
>>> +    sps->constraint_set_flags |= get_bits1(&gb) << 2; //
>>> constraint_set2_flag
>>> +    sps->constraint_set_flags |= get_bits1(&gb) << 3; //
>>> constraint_set3_flag
>>> +    sps->constraint_set_flags |= get_bits1(&gb) << 4; //
>>> constraint_set4_flag
>>> +    sps->constraint_set_flags |= get_bits1(&gb) << 5; //
>>> constraint_set5_flag
>>
>> Why not just get 6 bits at once?
>
> That’s how it’s done in h264_ps.c currently.
>
>>> +static void mxf_write_local_tags(AVIOContext *pb, const MXFLocalTagPair
>>> *local_tags, int count)
>>> +{
>>> +    int i;
>>> +    for (i = 0; i < count; i++) {
>>> +        avio_wb16(pb, local_tags[i].local_tag);
>>> +        avio_write(pb, local_tags[i].uid, 16);
>>> +    }
>>> +}
>>
>> This function could be used to simplify mxf_write_primer_pack(). But
>> that probably belongs in a separate patch.
>
> Yes, it does
>
>>> +
>>>  static void mxf_write_primer_pack(AVFormatContext *s)
>>>  {
>>>      MXFContext *mxf = s->priv_data;
>>>      AVIOContext *pb = s->pb;
>>>      int local_tag_number, i = 0;
>>> +    int avc_tags_count = 0;
>>>
>>>      local_tag_number = FF_ARRAY_ELEMS(mxf_local_tag_batch);
>>>      local_tag_number += mxf->store_user_comments *
>>> FF_ARRAY_ELEMS(mxf_user_comments_local_tag);
>>>
>>> +    for (i = 0; i < s->nb_streams; i++) {
>>> +        MXFStreamContext *sc = s->streams[i]->priv_data;
>>> +        if (s->streams[i]->codecpar->codec_id == AV_CODEC_ID_H264 &&
>>> !sc->avc_intra) {
>>> +            avc_tags_count =
>>> FF_ARRAY_ELEMS(mxf_avc_subdescriptor_local_tags);
>>> +            local_tag_number += avc_tags_count;
>>
>> This will output a broken file if there's more than one XAVC stream.
>> Not possible now I think, but will be a problem is someone decides to
>> give higher operational patterns a try
>
> Yes, it will get caught when this happens.
>
> —
> Baptiste
>
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