Re: [FFmpeg-devel] [PATCH] avformat/avcodec: Add DTS-UHD demuxer and parser, movenc support.

[Paul B Mahol <onemda@gmail.com>]

On Wed, Jun 14, 2023 at 7:37 AM Paul B Mahol <onemda@gmail.com> wrote:

>
>
> On Wed, Jun 14, 2023 at 2:00 AM Roy Funderburk <royffmpeg@funderburk.us>
> wrote:
>
>>
>> On 6/13/23 11:35 AM, Paul B Mahol wrote:
>> > Doing allocation in probe?
>> > Probing should be very fast.
>>
>> In line 143 of the avformat patch, memory allocation is removed from the
>> probe
>>
>> >>+int dtsuhd_frame(DTSUHD *h, const uint8_t *data, size_t data_bytes,
>> >>+                DTSUHDFrameInfo *fi, DTSUHDDescriptorInfo *di)
>> >>+{
>> >>+    gb = &h->gb;
>> >>+    init_get_bits(gb, data, data_bytes * 8);
>> > init_get_bits8, and check return code.
>>
>> In line 986 of the avcodec patch, changed to using init_get_bits8 and
>> added return code check.
>>
>> >>+        fi->sync = h->is_sync_frame;
>> >>+        fi->frame_bytes = h->frame_bytes;
>> >>+        fi->sample_rate = h->sample_rate;
>> >>+        fi->sample_count = (h->frame_duration * fi->sample_rate)
>> /(h->clock_rate * fraction);
>> >>+        fi->duration = (double)fi->sample_count / fi->sample_rate;
>> >Please  no double  type.
>> >Also make use of av_rescale.
>>
>> Around line 1108 of the avcodec patch, I found the duration was not
>> needed and removed it.
>>
>>
>> On 6/13/23 12:04 PM, Anton Khirnov wrote:
>> > Also do note that sharing structs across libraries opens you to various
>> > compatibility questions [2]. It might be easier to sidestep them by
>> > having a function in libavcodec that accepts AVCodecParameters and fills
>> > them according to the data, rather than pass codec-specific structs
>> > between libavformat and libavcodec.
>>
>> In line 1061 of the avcodec patch, changed the function to:
>>   int av_dtsuhd_frame(DTSUHD *h, const uint8_t *data, size_t data_bytes,
>>         AVCodecParameters *codecpar, uint8_t **udts, int *udts_size)
>>
>>
>>
> Usually libavcodec code does use get_vlc2() for variable length codes,
> instead of
> usage of show_bits/skip_bits/get_bits.
>
>
Also there is no reason to use int for elements in tables when max value
can be lower.
Current table reading/handling code should be completely rewritten to use
get_vlc2().
And tables split so length of codes use uint8_t type.


>
>
>
>>
>> Thank you for reviewing this,
>> -Roy_______________________________________________
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>
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