Trim some codecs from FFmpeg build

[JanuszL]

No description provided.

[greptile-apps]

Greptile Summary

This PR extends the existing selective FFmpeg codec trimming by disabling five additional software decoders — hevc, h264, aac, aac_fixed, and aac_latm — from the bundled FFmpeg build. The intent is to reduce binary size and unused code surface, consistent with DALI's GPU-centric (NVDEC) decode pipeline that never calls these software decoders.

• hevc and h264 software decoders are disabled while hevc_mp4toannexb and h264_mp4toannexb BSFs remain enabled; this is the correct setup for an NVDEC path, but could affect stream probing (avformat_find_stream_info) or break CPU-only environments entirely.
• aac, aac_fixed, and aac_latm audio decoders are removed; safe assuming DALI does not need audio decode (aligns with typical DALI usage for video frames only).

Confidence Score: 4/5

The change is straightforward and follows the established pattern in this build script; the main risk is that disabling software H.264/HEVC decoders could break CPU-only environments or FFmpeg stream probing, but those are unlikely scenarios for a GPU-first library like DALI.

The five new --disable-decoder flags are consistent with the existing selective-disable approach. The AAC removals look clean. The H.264/HEVC removals are paired correctly with the BSFs needed for NVDEC, but removing the software decoders eliminates any CPU fallback path and could interfere with avformat_find_stream_info stream probing on H.264/HEVC content.

build_scripts/build_ffmpeg.sh — specifically the interaction between the newly disabled h264/hevc decoders and the still-enabled h264_mp4toannexb/hevc_mp4toannexb BSFs warrants a second look if DALI has any CPU-only test paths.

Important Files Changed

Filename	Overview
build_scripts/build_ffmpeg.sh	Adds five --disable-decoder flags (hevc, h264, aac, aac_fixed, aac_latm) to the FFmpeg configure step; consistent with existing selective-disable pattern but removes software fallback for the two video codecs whose BSFs are still actively enabled.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Video File / Container] --> B[avformat demuxer\nenabled]
    B --> C{Codec type}
    C -->|H.264| D[h264_mp4toannexb BSF\nenabled]
    C -->|HEVC| E[hevc_mp4toannexb BSF\nenabled]
    C -->|AAC Audio| F[AAC SW Decoder\ndisabled: aac / aac_fixed / aac_latm]
    D --> G[NVDEC Hardware Decoder\ngpu path]
    E --> G
    C -->|H.264 SW decode| H[H.264 SW Decoder\ndisabled: h264]
    C -->|HEVC SW decode| I[HEVC SW Decoder\ndisabled: hevc]
    style F fill:#f99,stroke:#c00
    style H fill:#f99,stroke:#c00
    style I fill:#f99,stroke:#c00
    style G fill:#9f9,stroke:#090

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[greptile-apps]

Software H.264/HEVC decoders disabled while BSFs remain enabled

The h264_mp4toannexb and hevc_mp4toannexb BSFs are kept (line 56), which suggests the pipeline routes these bitstreams to a hardware decoder (NVDEC). Disabling the software decoders is therefore intentional for the GPU path. However, if FFmpeg calls avformat_find_stream_info() internally — which DALI's demuxer likely does — FFmpeg may attempt to probe the stream by decoding a few packets using the software decoder. With both hevc and h264 decoders disabled, probing such streams could yield incomplete or inaccurate stream metadata (e.g., missing width/height, frame rate, or pixel format). This is also a hard break for any CPU-only test or CI environment that exercises the video decode path without NVDEC available.

[JanuszL]

The DALI side rework will be done in a separate PR to the DLAI repo itself. This is fully intentional.

[JanuszL]

Related to NVIDIA/DALI#6352.