[FFmpeg-devel] [PATCH v23 04/10] avformat/evc_demuxer: Added demuxer to handle reading EVC video files
Dawid Kozinski/Multimedia (PLT) /SRPOL/Staff Engineer/Samsung Electronics
d.kozinski at samsung.com
Wed Jun 7 19:30:14 EEST 2023
> -----Original Message-----
> From: Dawid Kozinski/Multimedia (PLT) /SRPOL/Staff Engineer/Samsung
> Electronics <d.kozinski at samsung.com>
> Sent: środa, 7 czerwca 2023 17:41
> To: 'FFmpeg development discussions and patches' <ffmpeg-
> devel at ffmpeg.org>
> Subject: RE: [FFmpeg-devel] [PATCH v23 04/10] avformat/evc_demuxer: Added
> demuxer to handle reading EVC video files
>
>
>
>
>
> > -----Original Message-----
> > From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> > James Almer
> > Sent: środa, 7 czerwca 2023 15:40
> > To: ffmpeg-devel at ffmpeg.org
> > Subject: Re: [FFmpeg-devel] [PATCH v23 04/10] avformat/evc_demuxer:
> > Added demuxer to handle reading EVC video files
> >
> > On 6/7/2023 10:36 AM, Dawid Kozinski/Multimedia (PLT) /SRPOL/Staff
> > Engineer/Samsung Electronics wrote:
> > >
> > >
> > >
> > >> -----Original Message-----
> > >> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> > >> James Almer
> > >> Sent: poniedziałek, 29 maja 2023 15:08
> > >> To: ffmpeg-devel at ffmpeg.org
> > >> Subject: Re: [FFmpeg-devel] [PATCH v23 04/10] avformat/evc_demuxer:
> > >> Added demuxer to handle reading EVC video files
> > >>
> > >> On 5/26/2023 7:31 AM, Dawid Kozinski wrote:
> > >>> +static int get_temporal_id(const uint8_t *bits, int bits_size) {
> > >>> + int temporal_id = 0;
> > >>> + short t = 0;
> > >>> +
> > >>> + if (bits_size >= EVC_NALU_HEADER_SIZE) {
> > >>> + unsigned char *p = (unsigned char *)bits;
> > >>> + // forbidden_zero_bit
> > >>> + if ((p[0] & 0x80) != 0)
> > >>> + return -1;
> > >>> +
> > >>> + for (int i = 0; i < EVC_NALU_HEADER_SIZE; i++)
> > >>> + t = (t << 8) | p[i];
> > >>
> > >> I think this can be replaced with AV_RB16.
> > >>
> > >>> +
> > >>> + temporal_id = (t >> 6) & 0x0007;
> > >>> + }
> > >>> +
> > >>> + return temporal_id;
> > >>> +}
> > >>
> > >> [...]
> > >>
> > >>> +static uint32_t read_nal_unit_length(const uint8_t *bits, int
> > >>> +bits_size) {
> > >>> + uint32_t nalu_len = 0;
> > >>> +
> > >>> + if (bits_size >= EVC_NALU_LENGTH_PREFIX_SIZE) {
> > >>> +
> > >>> + int t = 0;
> > >>> + unsigned char *p = (unsigned char *)bits;
> > >>> +
> > >>> + for (int i = 0; i < EVC_NALU_LENGTH_PREFIX_SIZE; i++)
> > >>> + t = (t << 8) | p[i];
> > >>
> > >> AV_RB32.
> > >>
> > >>> +
> > >>> + nalu_len = t;
> > >>> + if (nalu_len == 0) // Invalid bitstream size
> > >>> + return 0;
> > >>> + }
> > >>> +
> > >>> + return nalu_len;
> > >>> +}
> > >>
> > >> [...]
> > >>
> > >>> +static int evc_frame_merge_filter(AVBSFContext *bsf, AVPacket *out) {
> > >>> + EVCMergeContext *ctx = bsf->priv_data;
> > >>> + AVPacket *in = ctx->in;
> > >>> +
> > >>> + int free_space = 0;
> > >>> + size_t nalu_size = 0;
> > >>> + uint8_t *nalu = NULL;
> > >>> + int au_end_found = 0;
> > >>> + int err;
> > >>> +
> > >>> + err = ff_bsf_get_packet_ref(bsf, in);
> > >>> + if (err < 0)
> > >>> + return err;
> > >>> +
> > >>> + nalu_size = read_nal_unit_length(in->data,
> > >> EVC_NALU_LENGTH_PREFIX_SIZE);
> > >>> + if(nalu_size <= 0) {
> > >>> + av_packet_unref(in);
> > >>> + return AVERROR_INVALIDDATA;
> > >>> + }
> > >>> +
> > >>> + nalu = in->data + EVC_NALU_LENGTH_PREFIX_SIZE;
> > >>> + nalu_size = in->size - EVC_NALU_LENGTH_PREFIX_SIZE;
> > >>> +
> > >>> + // NAL unit parsing needed to determine if end of AU was found
> > >>> + err = parse_nal_unit(nalu, nalu_size, bsf);
> > >>> + if (err < 0) {
> > >>> + av_log(bsf, AV_LOG_ERROR, "NAL Unit parsing error\n");
> > >>> + av_packet_unref(in);
> > >>> +
> > >>> + return err;
> > >>> + }
> > >>> +
> > >>> + au_end_found = end_of_access_unit_found(bsf);
> > >>> +
> > >>> + free_space = ctx->au_buffer.capacity - ctx->au_buffer.data_size;
> > >>> + while( free_space < in->size ) {
> > >>> + ctx->au_buffer.capacity *= 2;
> > >>> + free_space = ctx->au_buffer.capacity -
> > >>> + ctx->au_buffer.data_size;
> > >>> +
> > >>> + if(free_space >= in->size) {
> > >>> + ctx->au_buffer.data = av_realloc(ctx->au_buffer.data,
> > >>> + ctx-
> > >>> au_buffer.capacity);
> > >>> + }
> > >>> + }
> > >>> +
> > >>> + memcpy(ctx->au_buffer.data + ctx->au_buffer.data_size,
> > >>> + in->data,
> > >>> + in->size);
> > >>
> > >> This is including the Annex-B's nal_unit_lenght value into the
> > >> assembled
> > > packet. I
> > >> assume libxevd expects this? Also, is it defined as part of the
> > >> ISOBMFF encapsulation? Patch 07/10 does not seem to strip it.
> > >
> > > Could you expand on this topic?
> > > What do you mean by "Patch 07/10 does not seem to strip it"?
> > > Patch 7/10 expands the implementation of the MOV Muxer to support
> > > the EVC stream.
> > > The function ff_isom_write_evcc parses the received data, extracts
> > > NAL units of types SPS, PPS, APS, SEI, and inserts their contents
> > > into the corresponding elements of the arrays array, which is a
> > > component of the EVCDecoderConfigurationRecord structure.
> > > Additionally, the ff_isom_write_evcc function populates the relevant
> > > fields of the EVCDecoderConfigurationRecord structure based on the
> > > parsed SPS NAL unit data, and then calls the evcc_write function,
> > > which writes the EVCDecoderConfigurationRecord to the stream.
> > >
> > > It seems that I don't understand what's wrong with our
> > > implementation ( I mean MOV muxer for EVC) and it seems I need your
> > > help in this matter. I need an explanation of what's wrong and what
> > > should be done to fix
> > the issue.
> >
> > I mean the packets that go into ISOBMFF Sample, not the evcc atom. Is
> > the encapsulation supposed to include the nal_unit_length from Annex-B?
>
> The function mov_write_single_packet(s, pkt) receives packets containing the
> Access Units (AU) of an EVC stream. Each AU consists of a sequence of NAL
> units, each preceded by a 4-byte prefix that contains information about the
> length of the NAL unit. The entire AU is then copied to AVIOContext using
> avio_write(pb, pkt->data, size).
>
It seems to me that everything is okay. If I am mistaken, just let me know.
As we have also completed all the fixes following your review this is the last thing blocking us from creating a new patchset.
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > https://protect2.fireeye.com/v1/url?k=64932a8f-05183fb9-6492a1c0-
> > 74fe485cbff1-9eaddc0975cfe99c&q=1&e=9bd489fd-4417-4f27-9fc0-
> >
> e7d04e51de8c&u=https%3A%2F%2Fffmpeg.org%2Fmailman%2Flistinfo%2Fffmp
> > eg-devel
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
More information about the ffmpeg-devel
mailing list