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[190.225.105.197]) by smtp.gmail.com with ESMTPSA id s3-20020a05687087c300b0017243edbe5bsm7371622oam.58.2023.05.10.13.20.39 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 May 2023 13:20:40 -0700 (PDT) Message-ID: <8e7891de-b73b-0a67-4127-3525ecd2a3f4@gmail.com> Date: Wed, 10 May 2023 17:20:55 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 Content-Language: en-US To: ffmpeg-devel@ffmpeg.org References: <20230427120245.1151-1-d.kozinski@samsung.com> From: James Almer In-Reply-To: <20230427120245.1151-1-d.kozinski@samsung.com> Subject: Re: [FFmpeg-devel] [PATCH v22 02/10] avcodec/evc_parser: Added parser implementation for EVC format X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: On 4/27/2023 9:02 AM, Dawid Kozinski wrote: > - Added constants definitions for EVC parser > - Provided NAL units parsing following ISO_IEC_23094-1 > - EVC parser registration > > Signed-off-by: Dawid Kozinski > --- > libavcodec/Makefile | 1 + > libavcodec/evc.h | 155 ++++ > libavcodec/evc_parser.c | 1497 +++++++++++++++++++++++++++++++++++++++ > libavcodec/parsers.c | 1 + > 4 files changed, 1654 insertions(+) > create mode 100644 libavcodec/evc.h > create mode 100644 libavcodec/evc_parser.c There seems to have been a regression in this version compared to v20. Try to compile with the libxevd decoder disabled and open a raw file (not mp4). Whereas with v20 i was getting > Input #0, evc, from 'akiyo_cif.evc': > Duration: N/A, bitrate: N/A > Stream #0:0: Video: evc (Baseline), none, 352x288, 25 fps, 25 tbr, 1200k tbn I'm now getting > Input #0, evc, from 'akiyo_cif.evc': > Duration: N/A, bitrate: N/A > Stream #0:0: Video: evc (Baseline), none, 555902582x0, 25 fps, 25 tbr, 1200k tbn It seems that the problem showed up because you moved the parameter sets to stack to skip allocating them, and you no longer check if they exist or were parsed by looking at slice_pic_parameter_set_id and such. That aside, i looked at the EVC spec and noticed that the "raw" format in Annex-B is unlike that of H.26{4,5,6}: There's no start code, and instead there's a NAL size prefix, which sounds like the isobmff way of encapsulating NALUs. I also noticed that the syntax for nal_unit() contains an emulation_prevention_three_byte element, but there's no explanation for it in the semantics section. Its existence in H.26* is to prevent parsers from misinterpreting a sequence of two or more zeroes as a potential start code, but that's clearly not the case here, so why is it defined and present at all? What this means is that the parser can't be made to assemble an AU. If you feed it data starting from the middle of a NAL, it will not be able to sync to the start of the next NAL because all it looks for is a four byte size value and will accept the very first four bytes its fed as one. Since i doubt the spec can be changed at this point to amend this oversight, the AU assembling will have to occur in the evc demuxer, much like we do with AV1 (both raw obu and Annex-B formats as defined in the corresponding spec), and the parser be limited to parse fully assembled NALs with parse_nal_units(). _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".